util: add _mesa_strtod and _mesa_strtof

Both core mesa and glsl have their own wrappers for strtof_l.  Merge
and move them to util/.  They are compiled with a C++ compiler so that
we can make them thread-safe in a following commit.

Signed-off-by: Chia-I Wu <olv@lunarg.com>
Reviewed-by: Kenneth Graunke <kenneth@whiteacpe.org>
10 files changed