Merge from glibc:

        * regex.c: Declare wcs functions only if compiling with
        MBS_SUPPORT.
        Don't use #elif for traditional C.

        * regex.c: Revamp memory allocation for WCHAR functions to
        not use too much stack.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@44471 138bc75d-0d04-0410-961f-82ee72b054a4