Import David Gay's gdtoa library.
* mingwex/gdtoa: New directory.
* mingwex/gdtoa/(arithchk.c, dmisc.c, dtoa.c, g__fmt.c, g_dfmt.c,
g_ffmt.c, g_xfmt.c, gd_arith.h, gd_qnan.h, gdtoa.c, gdtoa.h,
gdtoaimp.h, gethex.c, gmisc.c, hd_init.c, hexnan.c, misc.c, qnan.c,
README, smisc.c, strtodg.c, strtodnrp.c, strtof.c, strtopx.c, sum.c,
ulp.c): New files.
* mingwex/(strtof.c, strtold.c, ldtoa.c): Remove files.
* mingwex/math/(cephes-emath.c, cephes-emath.h): Remove files.
* mingwex/mb_wc_common.h (get_cp_from_locale); Rename to get_codepage().
* mingwex/(btowc.c, wctob.c, mbrtowc.c, wcrtomb.c): Adjust call to get_codepage().
* mingwex/wcstold.c: Avoid using strtold internals.
* mingwex/wcstof.c: Rewrite.
* mingwex/Makefile.in (GDTOA_DISTFILES): Add to distribution.
(GDTOA_OBJS): Add to library.
(DISTFILES): Remove strtof.c strtold.c ldtoa.c cephes-emath.c cephes-emath.h.
(STDLIB_OBJS): Remove.
(STDLIB_STUB_OBJS): Remove strtof.o wcstof,o.
(Q8_OBJS): Add wcstof.o wcstold.o.
* include/stdlib.h (strtof): Remove inline definition.
(wcstof): Likewise.
* include/wchar.h (wcstof): Remove inline definition.
