* Cleaned up UI_interface.h a bit, and added some comments to
organize things a bit and indicate what should be used when.
* uiMenu* functions can now be used to create menus for headers
too, this is done with a uiDefMenuBut, which takes a pointer
to a uiMenuCreateFunc, that will then call uiMenu* functions.
* Renamed uiMenuBegin/End to uiPupMenuBegin/End, as these are
specific to making popup menus. Will convert the other
conformation popup menu functions to use this too so we can
remove some code.
* Extended uiMenu functions, now there is is also:
BooleanO, FloatO, BooleanR, EnumR, LevelEnumR, Separator.
* Converted image window headers to use uiMenu functions, simplifies
menu code further here. Did not remove the uiDefMenu functions as
they are used in sequencer/view3d in some places now (will fix).
* Also tried to simplify and fix bounds computation a bit better
for popup menus. It tried to find out in advance what the size
of the menu was but this is difficult with keymap strings in
there, now uiPopupBoundsBlock can figure this out afterwards and
ensure the popup is within the window bounds. Will convert some
other functions to use this too.
Timers: added extra 'event type' argument to call to add a timer:
WM_event_add_window_timer(win, event_type, interval)
This way other timer systems don't generate overhead on the queues.
(button timers were creating unused animation-playback operators)
* API and usage is basically the same still.
* Panels were moved to region level. I first thought of keeping them at area
level, but having them at region level it's simpler to handle events and do
drawing, and also to integrate with view2d. They can still become area level
overlapping regions, if we make a floating (or docked) region that can
contain panels.
* Added back a few panels from the scene buttons for testing.
Issues still:
* The view2d handling and alignment refresh of panels is not correct yet in the
buttons window.
* I did not yet bring back the block handlers system. It was basically a system
that stored which panel was open and where the events for that panel would go.
Just a few functions, but not sure how it fits in 2.5.
* There was a case where dragging panels would not properly remove the window
level handler, but could not redo anymore even though I don't think I fixed
it.
* Some text in the panels goes past the end of the button, that is due to the
checkmark button drawing, not related to this commit.
Other UI code changes:
* Renamed interface.h to interface_intern.h for consistency.
* Fixed some issues with freeing of blocks when they changed due to context.
* uiDrawBlock now takes a context pointer (mostly for block drawextra).
