Debugger: Fix metaobject lookuop for older versions of GDB

Symbol.value is not available in 7.4

Change-Id: I86e00cbeef61669ca5950e35a7b0aed86dcb2f87
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Debugger: Re-work qt namespace detection with gdb

We can always use python now. Avoids one roundtrip on startup,
a temporary file, and only does it when needed.

Change-Id: Id32a812bec477307da1d93950f7758f3a5699464
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>