Rewritten Qt4 paint core to avoid full redraws.
Update year in mpv_qk_common.cpp copyright header.
Stop calling update() from keyReleaseEvent().
Minor code cleaning.
Moved class MPArea definition to mpv_qk_common.cpp.
Do not optimize mp_draw() if the qpixmap has changed.
Update year in mpv_qt4.cpp and mpv_kde4.cpp copyright header.