Another step in the undo evolution.

- Made unified API for undo calls, to be found in space.c
  BIF_undo_push(char *str)
  BIF_undo(void)
  BIF_redo(void)
  These calls will do all undo levels, including editmode and vpaint.

  The transition is work in progress, because mesh undo needs recode.

- New global hotkey CTR+Z for undo
  Note: 'shaded draw mode' still is SHIFT+Z, the old CTRL+Z was to recalc
  the lighting in shaded mode, which already became much more interactive,
  like during/after any transform().
  Recalc hotkey now is SHIFT+ALT+Z

  CTRL+<any modifier>+Z is redo.

- For OSX users; the Apple-key ("Command") now maps to CTRL as well. This
  disables the one-mouse-button hack for rightmouse btw, will be fixed in
  next commit. At least we can use Apple-Z :)

- Old Ukey for undo is still there, as a training period... my preference is
  to restore Ukey to "reload original data" as in past, and only use new
  CTRL+Z for undo.

- Added undo_push() for all of editobject.c and editview.c. Meaning we can
  start using/testing global undo in the 3d window. Please dont comment on
  missing parts for now, first I want someone to volunteer to tackle all of
  that.

- Since the global undo has a full 'file' in memory, it can save extremely
  fast on exit to <temp dir>/quit.blend. That's default now when global undo
  is enabled. It prints "Saved session recovery to ..." in console then.

- In file menu, a new option is added "Recover Last Session". Note that this
  reads the undo-save, which is without UI.

- With such nice new features we then can also kill the disputed
  Cancel/Confirm menu on Q-KEY.

- Added fix which initializes seam/normal theme color on saved themes.
  They showed black now.... (Note: that's in usiblender.c!)

source/blender/src/interface.c

@@ -3091,8 +3091,9 @@ static int ui_do_block(uiBlock *block, uiEvent *uevent)
 					if(inside || uevent->event!=LEFTMOUSE) {
 						butevent= ui_do_button(block, but, uevent);
 						
-						if(but->type!=BLOCK && but->type!=MENU) BIF_write_undo(but->str);
-
+						if( !(block->flag & UI_BLOCK_LOOP))
+							if(but->type!=BLOCK && but->type!=MENU) BIF_undo_push(but->str);
+				
 						if(butevent) addqueue(block->winq, UI_BUT_EVENT, (short)butevent);
 
 						/* i doubt about the next line! */