clapack: new package

This package provides BLAS and LAPACK libraries.

Though it is common to find implementation of these two libraries in
Fortran, this package provides a C-implementation for both, because:
- Fortran support has been deprecated in Buildroot since the 2013.11
  release;
- most of the external toolchains do not provide a Fortran compiler.

Often BLAS build-systems build some test programs and run them to
generate some source files or adjust some build optimizations, naively
assuming they are building the library for the build-machine. This does
not play well when cross-compiling.

This implementation has this defect too, by building and running a tool
generating a header.
However, the build-system allows to pass an empty header.
So, we have to patch the CMake to build the generator (but never
install it) and correctly support building with and without this header
provided by the user.

Also, some CMake patches are needed to fix the build and install rules.

[Peter: needs largefile, fix _LICENSE_FILES, tweak patch desc]
Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>