bind: Add libxml2 support.

* Created packageconfig for libxml2 so that we can properly set all the option.
* Bind package has the option to build with libxml but it's configure script was
  written in such a way that it was looking for a xml2-config file in bin folder.
  We provide sysroot path in --with-libxml2 option but we dont have bin folder
  in sysroot. So it does not find the xml2-config file. So configure script says
  that it did not find libxml stuff. Add a patch to update configure.in script to
  use pkg-config to get the libxml lib and cflag information.
* Add pkgconfig-ntive in inherit as we are using pkg-config in confure script.
* JIRA SB-4116

Signed-off-by: Noor Ahsan <noor_ahsan@mentor.com>