chown: detect Solaris and FreeBSD bug Solaris 9 and FreeBSD 7.2 chown("link-to-file/",uid,gid) mistakenly changes ownership of "file". * lib/chown.c (rpl_chown): Work around bug. * m4/chown.m4 (gl_FUNC_CHOWN): Check for trailing slash bugs. (gl_PREREQ_CHOWN): Delete. * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Add witness. * modules/unistd (Makefile.am): Populate it. * lib/unistd.in.h (chown): Update declaration. * lib/lchown.c (chown): Update client. * modules/lchown (Depends-on): Add lstat. * doc/posix-functions/chown.texi (chown): Document the bug. * doc/posix-functions/getgroups.texi (getgroups): Document getgroups pitfall. * modules/chown-tests: New file. * tests/test-chown.h (test_chown): Likewise. * tests/test-chown.c (main): Likewise. Signed-off-by: Eric Blake <ebb9@byu.net>