x11-toolkits/py-wxPython30: Unbreak on F8 and F9

This port must be built under c++11 standard like the rest of the
wx-dependent ports. I couldn't find a way to pass the flag so I had
to patch the python script directly. Also, the USES=compiler setting
was missing, which is required to actually pull in a c++11 capable
compiler on the older FreeBSD releases.

This port was blocking ~29 other ports from building on releases that
it wouldn't build on.

Approved by: blanket