Upgrade to expat 2.1.1

Modified the import_expat.sh script as the archive is now
compressed using bzip2 instead of gzip and uses configure.ac
instead of configure.in.

Modified README.android to make the example command up to date
with respect to the new archive format and also to ensure that
it builds dependencies.

All the remaining changes are straight from upstream.

Bug: 27818751

(cherry picked from commit cee23496d017f13eccc125e2ab7044de53dec8da)

Change-Id: Ic75a6c455dbcc34aaa7c30c109dc1565c5c52b04
(cherry picked from commit c05e032be5350e70e721727a96d5d4309f74af01)
14 files changed