Add _PC_CASE_INSENSITIVE to [f]pathconf

Update the getconf utility to support the new flag as well as
_PC_POSIX_PERMISSIONS and _PC_POSIX_SECURITY.  These were previously
unsupported, probably as an oversight.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/fhandler.cc

@@ -1891,6 +1891,8 @@ fhandler_base::fpathconf (int v)
 	return pc.has_acls () || pc.fs_is_nfs ();
       set_errno (EINVAL);
       break;
+    case _PC_CASE_INSENSITIVE:
+      return !!pc.objcaseinsensitive ();
     default:
       set_errno (EINVAL);
       break;