* lib/stdlib.in.h (strtof): New declaration.
* lib/strtod.c: Support USE_FLOAT.
* lib/strtof.c: New file.
* m4/strtof.m4: New file, based on m4/strtod.m4.
* m4/ldexpf.m4 (gl_CHECK_LDEXPF_NO_LIBM): New macro, based on
m4/ldexp.m4.
* m4/stdlib_h.m4 (gl_STDLIB_H_REQUIRE_DEFAULTS): Initialize
GNULIB_STRTOF.
* modules/stdlib (Makefile.am): Substitute GNULIB_STRTOF, HAVE_STRTOF,
REPLACE_STRTOF.
* modules/strtof: New file.
* tests/test-stdlib-c++.cc (strtof): Check signature.
* doc/posix-functions/strtof.texi: Mention the new module and the bugs
that it fixes.
(gl_STDLIB_H_DEFAULTS): Initialize HAVE_STRTOF, REPLACE_STRTOF.