* lib/math.in.h (ldexp): New declaration.
* lib/ldexp.c: New file, based on lib/ldexpl.c.
* lib/ldexpl.c: Moved the implementation to lib/ldexp.c. Just include
it.
* m4/math_h.m4 (gl_MATH_H_REQUIRE_DEFAULTS): Initialize GNULIB_LDEXP.
(gl_MATH_H_DEFAULTS): Initialize REPLACE_LDEXP.
* m4/ldexp.m4 (gl_FUNC_LDEXP): Require gl_MATH_H_DEFAULTS and
gl_FUNC_ISNAND. Invoke gl_FUNC_LDEXP_WORKS. Set REPLACE_LDEXP. Consider
it when setting LDEXP_LIBM.
(gl_FUNC_LDEXP_WORKS): New macro.
* modules/math (Makefile.am): Substitute GNULIB_LDEXP, REPLACE_LDEXP.
* modules/ldexp (Files): Add lib/ldexp.c.
(Depends-on): Add math, isnand.
(configure.ac): Set GL_COND_OBJ_LDEXP. Invoke gl_MATH_MODULE_INDICATOR.
(Makefile.am): Conditionally compile ldexp.c.
* modules/ldexpl (Files): Add lib/ldexp.c.
* doc/posix-functions/ldexp.texi: Mention the OpenBSD bug.