My Debian wheezy LTS system is still on glibc 2.13; and LTS
distros may use older glibc, still, so lets not unnecessarily
break things out-of-the-box.
We seem to assume Linux is using glibc in our Makefiles anyways,
so I don't think this will introduce new breakage for users of
alternative libc implementations.
Signed-off-by: Eric Wong <e@80x24.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>