Problem reported by David Seifert in:
http://lists.gnu.org/archive/html/bug-gnulib/2016-06/msg00005.html
* NEWS, doc/posix-headers/stdbool.texi (stdbool.h): Document this.
* m4/stdbool.m4 (AC_CHECK_HEADER_STDBOOL): Make the check
more-forgiving for C++, in that it requires only 'bool'. Be a bit
stricter about checking that bool and _Bool are compatible in C.
Solaris 9 CC has a bug; it allows (int)0.0 and (bool)0 in constant
expressions, but not (bool)0.0. Our replacement stdbool cannot
provide that guarantee of C99 for this particular compiler, but
since use of that feature causes compilation failure rather than
silent mis-compilation, we just skip the test.
* tests/test-stdbool.c (f): Skip test that causes compilation
error under buggy C++ compiler.
* lib/stdbool.in.h: Document the limitation.
* doc/posix-headers/stdbool.texi (stdbool.h): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
