Debugger: Select topmost frame with usable data also with LLDB

Task-number: QTCREATORBUG-11597
Change-Id: I5d95c9172e90b82f5671427283cf46e924456c4c
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
TextEditors: remove unused variables

Change-Id: Id0d2115c7d8819d35dc626d5605650f7b450ee87
Reviewed-by: David Schulz <david.schulz@digia.com>