Copy xapian-{core,bindings,omega} and Search-Xapian from gentoo-x86
Version bump: xapian 1.2.13
Version bump: xapian-bindings 1.2.13
Support php 5.4

Also add note about subclassing Xapian,
see http://trac.xapian.org/wiki/ReleaseOverview/1.2.13
Version bump: xapian-omega 1.2.13
Version bump: Search-Xapian 1.2.13.0