* lib/c-strtod.c: Include <langinfo.h>, c-ctype.h.
(decimal_point_char): New function, copied from lib/vasnprintf.c.
(C_STRTOD): On platforms that don't have STRTOD_L nor a working
uselocale(), pre-parse the number and call STRTOD after having replaced
the '.' with the locale-dependent decimal point character.
* m4/c-strtod.m4 (gl_C_STRTOD, gl_C_STRTOLD): Test for nl_langinfo().
* modules/c-strtod (Depends-on): Add c-ctype. Remove strdup-posix.
* modules/c-strtold (Depends-on): Likewise.