[Lazarus] Mouse multi click rewritten

[Ondrej Pokorny]

Today I rewrote multiple click handling of the LCL. The reason for it 
was that every widgetset used its own code and logic and thus they 
behaved differently and also the maintainance was hard. Now the logic is 
in one function for every widget in Controls.pp CheckMouseButtonDownUp.

I updated the following WS to use the unified code: win32, qt, gtk2.
I will also update (or at least try to) update Carbon and Cocoa. For 
now, they use their own code/logic and behave slightly different from 
other WS.

It was quite a big change and nobody is perfect so please if you find 
any regressions regarding the mouse (popup menu not showing, not 
receiving mouse messages or receiving double mouse messages etc.), 
report them.

Ondrej