This will ultimately unlock the use of latest versions of
gcc 12, then gcc 13, and finally gcc 14.
Gcc 14 will unlock more testing.
This PR does not update version of gcc yet, just to make sure
old version still pass tests.
Remove some expensive tests.

Error: va_list 'ap2' was opened but not closed by va_end().

Error: memleakOnRealloc
Fix: Free is realloc fails (and at end of main).

Error: integer overflow
Fix: Use appropriate intermediate type. UL should be big enough
     on all platforms.

Error: uninitialized variables
Fix: Only use mpfr_zinit when mpfr_t already initialized
Note: The use of mpfr_zinit is inconsistent anyway.
      Gencoef needs a big cleanup and possibly porting to CMake

Deleted old benchmark system and replaced with most up to date one
which uses googlebench.
Changes to CMakeLists were carried accordingly.
Deleted section in documentation on legacy benchmark system.

Used to be scalar, now is sve.

When benchmarks are built, SLEEF_ENABLE_CXX should be
set to ON, since they use cpp.

Calls to functions which return two values (for example sincos),
were being optimized away in new benchmark tool. Fixed by
decreasing optimization level (O3 -> O2).

Add paragraph on multiple output format feature.

This patch fixes the following two problems:

* On aarch32, cbrt(4) was returned instead of M_PI/2 when +-INFINITY is given to atanf.
* Due to a bug in gcc-13, sign of tanf(+-0) was wrong on PUREC_SCALAR and VXE.

This patch also adds testing for the first problem.
The second problem is detected by the existing tester.

---------

Co-authored-by: Naoki Shibata <shibatch.sf.net@gmail.com>

Added new benchmark tool to SLEEF project using googlebench
framework.
In theory this tool can benchmark any unary and binary function
in SLEEF.
Benchmark is enabled in all functions listed in benchsleef.cpp.
This list uses macros in benchmark_callers.cpp, so that we can
enable benchmarking in multiple precisions using single lines
of code. It is also possible to list the exact function we want,
as each of the macros in benchmark_callers.cpp can be called
independently and connected like building blocks.
The tool is integrated with SLEEF via CMake, meaning it can
be built automatically when SLEEF is built. To enable that,
pass CMake argument -DSLEEF_BUILD_BENCH=ON.

This tool depends on C++17 standard.
Tested on aarch64 for scalar, vector and SVE routines
Tested on x86 for different vector length extensions.
Tested for llvm-17, gcc-11 and gcc-14.

It adds explicit typecasting so that C++ compilers can compile the inline headers generated from these helpers.

Co-authored-by: Naoki Shibata <shibatch.sf.net@gmail.com>

Propagate change from #489 to quad-tester.

Manually rebased.

Co-authored-by: Naoki Shibata <shibatch.sf.net@gmail.com>

same

Bump version to 3.6.1, as this version has a compatibility fix.

Add a new workflow to detect unexpected backward-incompatible
changes at precommit, by comparing current version against a
reference version, both generated on Linux with gcc.
It uses abidiff to compare ELF-format shared libraries.
This is the tool used by Fedora to report a recent breach in
API #534. Test should fail until it is fixed by #545.

Documentation for these runners here https://gitlab.arm.com/tooling/gha-runner-docs
Note that only SLEEF upstream repo is allowed to use these runners.

Integrate runners via strategy.matrix.os, in order to facilitate customisation
of step (e.g. config) based on runner label.

Install OpenSSL since tester3 is enforced.
New runners do not seem to come with openssl or cmake pre-installed.

Use SVE enabled instances (c7g)
Use 2xlarge instances so tests run slightly faster without compromising on availability.

Remove aarch64 from cross build and tests (on Linux).
And update documentation/README.

Define a custom style classes for dates and posts.

Bump version in CMakeLists.

Only Linux supports the AArch64 vector ABI, so it doesn't make sense
to expose these symbols anywhere else for AArch64. Without any
compelling reason to provide them on x86_64, it is better to just
revert this patch and deal with this more carefully after the release.

This reverts commit 0e47fcc3.

Restructured some of the sentences and added commands to
install dependencies for sleef's internal microbenchmark tool.

The acosh function is only defined for values greater or
equal to 1. Documentation was updated according to this.
Also, rephrased a confusing sentence.

Store the result of the function call during its benchmark
to prevent it from being optimized away.
Also changed name of NITER1 and NITER2 macros to more obvious
acronymes.
Tested on aarch64 and x86 so far.

Remove unsused css files.
Fix up name of branch to deploy.

Add a CONTRIBUTING.md and a section in the docs on contributing.
Rm CONTRIBUTORS.md because it is outdated, redundant with Github stats
and hard to maintain with the large amount of new contributors.

Kept the PR template simple to not demotivate people from contributing,
it could be improved with specialized templates in the future if
necessary.
In order to improve bug reports, we offer several templates for
filing issues/bugs.

The website is now rendered to html using https://just-the-docs.com/
template, thus providing navigation menu and search engine.
Sections' landing pages are rendered in Github UI (section/README.md)
and on website (section/index.html).
Links to other pages work in both Github and website thanks to permalinks.
Move images to img/ and sources to src/

* Enable GNUABI build on more targets #525

Previously SLEEF_BUILD_GNUABI_LIBS was silently ignored except for a
small number of targets, or if the compiler does not support weak
aliases.

It can now be built regardless of OS and compiler on AArch64 and
x86_64 - trying to enable it on any other target is now an error.

The GLIBC *_finite symbols are handled using the same workaround as is
used for the DALIAS macro when compiling on a target which does not
support aliases. Though in practice these symbols are unlikely to be
required on systems where aliases are unsupported, they are part of
the API so need adding, if just to make the tests build.

Also removed two CMake variables:
- ENABLE_ALIAS, which was unused
- ENABLE_GNUABI, which was now redundant but could still be forced on,
  leading to cryptic build failures
Both names are still used by the preprocessor in sleefsimd* sources
for managing names and aliases.

* Fix masked GNUABI build for NOALIAS

Masked symbols also need to sidestep aliases when they are not
supported.

* Disable GNUABI for unsupported targets in precommit

Default is on, but this setting was previously just ignored when
unsupported. Disable it in the failing pipelines.

Disable manual trigger to avoid spams.
Only run slow tests (like test-cross) on post-commit.
Display status of main GHA tests in README's test matrix,
so test that may fail in post-commit appear clearly in docs.

Bump version in CMakeLists.

Update/fix website.
And a link in markdown doc.
Give more useful cmake command, e.g. static/shared libs.
Fix documented uninstall commands.