Added the macro chk_connect_X for checking work of function QObject::connect() [Proposal]

This Merge-Request is a proposal to test the function QObject::connect(). Using the chk_connect_X macro, I was able to localize the connection problem DiffTextWindow::mVScrollBar in less than a minute. (See commit 3d535d60). Qt5 now has its own methods for validating a signal/slot connection (my macro was created when Qt5 did not exist yet). No matter what approach is used, the main thing is that it be. This helped me several times when looking for unpleasant "long-playing" errors