libxml2: upgrade to 2.9.2

libxml2: upgrade to 2.9.2

- Rebase python-sitepackages-dir.patch to 2.9.2

- Drop libxml2-CVE-2014-3660.patch which has been merged to 2.9.2.

- Add configure.ac-fix-cross-compiling-warning.patch to fix cross
  compilation failure.

- Tweak do_configure_prepend, use configure.ac to instead of configure.in

- Add cmake files to ${PN}-dev

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>