log10l: Work around AIX 5.1, IRIX 6.5, OSF/1 5.1 bug.

log10l: Work around AIX 5.1, IRIX 6.5, OSF/1 5.1 bug.

* lib/math.in.h (log10l): Override if REPLACE_LOG10L is 1.
* lib/log10l.c (log10l): If log10l exists, use it and provide just the
workaround.
* m4/log10l.m4 (gl_FUNC_LOG10L_WORKS): New macro.
(gl_FUNC_LOG10L): Invoke it. Set REPLACE_LOG10L.
* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_LOG10L.
* modules/math (Makefile.am): Substitute REPLACE_LOG10L.
* modules/log10l (configure.ac): Consider REPLACE_LOG10L.
(Depends-on): Update conditions.
* doc/posix-functions/log10l.texi: Mention the MSVC9, AIX 5.1,
IRIX 6.5, OSF/1 5.1 problems.