Apache httpd 2.4 support

These changes are copied from [FreeBSD ports](https://svnweb.freebsd.org/ports?view=revision&revision=364349). The FreeBSD author [copied from Debian](https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=179710), but that repository is no longer present on GitHub.

With these patches, I can build the tip of the `precise` branch for RHEL 6 and RHEL 7.