Debugger: Try to extract Qt version from QtCore

This won't work without inferior calls (e.g. when loading core files),
so the old code is needed as fallback.

Change-Id: I1c9efc06374b00bc391bf55528546ccefc60349b
Reviewed-by: hjk <hjk121@nokiamail.com>
Debugger: Adjust QDateTime dumper after Qt 5.2 changes

Task-number: QTCREATORBUG-10232
Change-Id: I10551a258edb9456c4a9f93a3bfb374a8f07fc7d
Reviewed-by: hjk <hjk121@nokiamail.com>
Debugger: Fix QVariant{Map,Hash} dumper with Qt 5

Change-Id: I5be3b960a7a3091dc77555883d93e3d89b17381d
Reviewed-by: hjk <hjk121@nokiamail.com>