Fix shared library support on Android.
This patch fixes two problems:
1) A libtool library created with the -release option and no -version-info
option was, when built with --enable-shared, installed without the
symlink libNAME.so -> libNAME-RELEASE.so. This led to subsequent failures
during "make install" of shared libraries that depend on it.
2) Executables were created without a RUNPATH property. These executables
then did not find their shared libraries when run.
* m4/libtool.m4: On Android, fix library_names_spec and
hardcode_libdir_flag_spec.