[Libguestfs] [PATCH 3/3] python: Allow bindings to be compiled with different version of libguestfs (RHBZ#1262983).

Patch to fix: https://bugzilla.redhat.com/show_bug.cgi?id=1262983 Note this won't help until the first two patches get backported to the stable branches, since <guestfs.h> won't define the necessary GUESTFS_HAVE_* macros. Rich.