Debugger: Fixes around watch editing.

assignValueInDebugger: Pass on WatchData as well, pass
on values as QVariant. Based on that, do more extensive
checks in CDB, preventing assignment of non-PODs.

Locals/Watch editing:
* Disable while running
* Edit pointer values as hex with validation.

CDB: Strip class types off reported pointer values and reformat
the values as short 0x-pointer values, introduce flag to
WatchData::source to do dumper expansion handling.

Windows: recognize int64 as int.

Register handler: Fix accessing uninitialized value.