gobject.py: Don't install frame filters when GDB does not support them

Stock GDB (both versions 7.0 and 7.1) does not come with the new
backtrace code and python API. To prevent an ugly python backtrace when
auto-loading gobject.py, let's catch the exception and not register the
FrameWrapper and the FrameFilter.

https://bugzilla.gnome.org/show_bug.cgi?id=613732