Debugger: Disable inapplicable context menu entries for sub-breakpoints

Task-Number: QTCREATORBUG-9984

Change-Id: Id4197b8d0db917606eb0e2767d2b05195e6cfbcd
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Fix compilation errors

Change-Id: I6b0d4956b5dcbd13ee26c72081f77e5d8a4f219b
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>