libmad: needs autoreconf

libmad uses a very old configure script.

When the toolchain lacks C++ and the build machine lacks /lib/cpp, this
old configure script fails because it can't find a C++ preprocessor that
is valid:

    checking for arm-buildroot-linux-uclibcgnueabi-g++... no
    checking whether we are using the GNU C++ compiler... no
    checking whether no accepts -g... no
    checking dependency style of no... none
    checking how to run the C++ preprocessor... /lib/cpp
    configure: error: C++ preprocessor "/lib/cpp" fails sanity check
    See `config.log' for more details.

This is yet another case that was tentatively fixed by bd39d11d
(core/infra: fix build on toolchain without C++), further amended by
4cd1ab15 (core: alternate solution to disable C++).

However, this only works on libtool scripts that are recent enough, and
thus we need to autoreconf to get it.

We also need to patch configure.ac so that it does not fail on the
missing, GNU-specific files: NEWS, AUTHORS, and Changelog.

Fixes:
 - http://autobuild.buildroot.org/results/6a6aa29295bd70679c3a22a149e79010fa20c1bf



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>