This is a copy of libxml2 2.7.7 and is used to create binaries
for PyObjC that do not have a dependency on the system version
of libxml2. This is needed to avoid problems when building on later
versions of OSX and running on earlier ones.

Libxml2 is not patched in any way, any issues in libxml2 will be
resolved upstreams and then merged here by copying a new release.

There is one change w.r.t. stock libxml2: this copy does not
include the subdirectories  "doc", "result" and "test" because these
aren't used by PyObjC and take up a lot of disk-space