Use RTLD_GLOBAL for the python-library.

Needed cause the QQmlExtensionPlugin is loaded
using RTLD_LOCAL and since python dynamic
loads additional libraries that may need to
access libpython API while they not load
the library themself its needed to make
sure libpython is loaded using RTLD_GLOBAL.

See http://forum.teamspeak.com/showthread.php/91916-RTLD_GLOBAL-in-dlopen-of-plugins-on-unix
for more background details.

This should fix the bug reported at
https://lists.launchpad.net/ubuntu-phone/msg04709.html