random_r: Override incompatible API on AIX, OSF/1.

random_r: Override incompatible API on AIX, OSF/1.

* lib/stdlib.in.h (random_r, srandom_r, initstate_r, setstate_r):
Override the system function if REPLACE_RANDOM_R is 1.
* m4/random_r.m4 (gl_FUNC_RANDOM_R): Require AC_CANONICAL_HOST. On AIX
and OSF/1, set REPLACE_RANDOM_R.
* m4/stdlib_h.m4 (gl_STDLIB_H_DEFAULTS): Initialize REPLACE_RANDOM_R.
* modules/stdlib (Makefile.am): Substitute REPLACE_RANDOM_R.
* modules/random_r (configure.ac): Test REPLACE_RANDOM_R.
* doc/glibc-functions/initstate_r.texi: Mention the AIX, OSF/1 problem.
* doc/glibc-functions/random_r.texi: Likewise.
* doc/glibc-functions/setstate_r.texi: Likewise.