intprops-test: suppress -Woverlength-strings Problem reported by Pádraig Brady in: http://lists.gnu.org/archive/html/bug-gnulib/2015-11/msg00008.html It is not worth the hassle to port this test to compilers that cannot handle long strings in diagnostics. * tests/test-intprops.c [__GNUC__]: Ignore -Woverlength-strings.