* QShortcut falls down on duplicates. It can have activatedAmbiguously
events, but these happen in arbitrary order and the shortcuts on
menu items just swallow the ambiguous activate so it's not useful.
* Instead we just let MainWindow pick up ShortcutOverride events and
consult a mapping of which shortcuts to use. We can use a smarter
selection method to choose the more 'local' shortcut if two shortcuts
that conflict exist.
* Unfortunately scintilla assumes its headers are all in the search path
so where possible we only add those folders when compiling scintilla
source, not our own.
* GUIInvoke helper changed to use QMetaObject::invokeMethod which works
on threads better.
* LambdaThread helper class now has a thread member, it doesn't derive
from thread (this seems to be recommended practice).
baldurk