* lib/math.in.h (sqrtf): New declaration.
* lib/sqrtf.c: New file.
* m4/sqrtf.m4: New file.
* m4/math_h.m4 (gl_MATH_H): Test whether sqrtf is declared.
(gl_MATH_H_DEFAULTS): Initialize GNULIB_SQRTF, HAVE_SQRTF.
* modules/math (Makefile.am): Substitute GNULIB_SQRTF, HAVE_SQRTF.
* modules/sqrtf: New file.
* tests/test-math-c++.cc: Check the declaration of sqrtf.
* doc/posix-functions/sqrtf.texi: Mention the new module.