This commit should hopefully fix all scrolling issues. As an added bonus, mouse scrol...

This commit should hopefully fix all scrolling issues. As an added bonus, mouse scrolling should be faster due to a deleted call to BufferView::update() that was not usefull (the important call to updateMetrics() is done in WorkArea()).

Log:
* BufferView/pimpl:
  - scrollDocView(): call to BufferView::update() deleted.
  - scrollDocView(): second part is now in setCursorFromScrollbar()
  - setCursorFromScrollbar(): new method.

* WorkArea:
  - setBufferView(): show the cursor immediately
  - redraw(): call to updateScrollbar()
  - updateScrollbar(): new method
  - scrollBufferView(): fix it and show the cursor immediately.

* qt4/GuiWorkArea
  - setScrollbarParams(): now disable the Qt scrollbar tracking.
  - paintEvent(): scrollbar related code deleted

* qt3/QWorkArea
  - setScrollbarParams(): now disable the Qt scrollbar tracking.

* qt3/QContentPane
  - paintEvent(): scrollbar related code deleted

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@14704 a592a061-630c-0410-9148-cb99ea01b6c8