getcwd: support coreutils better

getcwd: support coreutils better

Like strtod, getcwd incorrectly referred to HAVE_RAW_DECL_GETCWD,
but this might not be correct in coreutils, which disables
the raw decl checks.  Problem reported by Nagendra in
<http://bugs.gnu.org/10305#192>.
* lib/getcwd.c (__getcwd): Do not depend on HAVE_RAW_DECL_GETCWD.
* m4/getcwd-path-max.m4 (gl_FUNC_GETCWD_PATH_MAX):
Test the getcwd function, not any macro, since getcwd.c wants the
function.
* m4/getcwd.m4 (gl_FUNC_GETCWD):
Don't define HAVE_MINIMALLY_WORKING_GETCWD if the code doesn't
compile, as might happen if there's a macro but no function.