determine whether we need to call InvalidateRect() with bErase of TRUE or
  FALSE.  Reduces background erases in non-text toolbars by 80-85%.
- Fixed button state not being updated properly when LBUTTONDOWN and cursor
  leaves the toolbar.
- Removed FIXME() in TOOLBAR_DrawString for btnPtr->iString == -1, replaced
  with a source code comment.
- Removed unecessary call to TOOLBAR_CalcToolbar() in
  TOOLBAR_GetItemRect().  Optimized TOOLBAR_CalcStrings(). Fixes very
  slow responding toolbars in Ultraedit due to processing TB_GETITEMRECT
  messages.
- Optimized TOOLBAR_SetIntent(), SetRows() and SetStyle().