I pushed this now (as there were no negative comments):
> 2010-09-28 Bruno Haible <[email protected]>
>
> New module 'system-posix'.
> * modules/system-posix: New file.
> * lib/stdlib.in.h: Include <sys/wait.h> only when the 'system-posix'
> module is present.
> * m4/stdlib_h.m4 (gl_STDLIB_H_DEFAULTS): Initialize
> GNULIB_SYSTEM_POSIX.
> * modules/stdlib (Depends-on): Remove sys_wait.
> (Makefile.am): Substitute GNULIB_SYSTEM_POSIX.
> * doc/posix-functions/system.texi: Mention the new module.
> * doc/posix-headers/stdlib.texi: Likewise.
> * tests/test-stdlib.c: If GNULIB_TEST_SYSTEM_POSIX is not defined,
> define test_sys_wait_macros to a no-op.
> Reported by Sam Steingold <[email protected]>.
