== Action Editor -> Auto-Snap ==

There's a new selection-box on the header of the action editor, which
sets the mode of auto-snapping for transforms. By default auto-snapping
is off.

There are 3 modes of auto-snap:
* Off - transforms per normal
* Frame Step - grid-step transform (may have errors with scaled actions)
* Nearest Frame - true snap-to-frame (takes into account nla-scaling)

These translate to the following hotkeys when transforming:
* Off - no keys press/held (as it's always been)
* Frame Step - Ctrl (as it's always been)
* Nearest Frame - Shift (replaces old shift-key behaviour which was not useful)

source/blender/src/header_action.c

@@ -1270,14 +1270,23 @@ void action_buttons(void)
 
 	uiClearButLock();
 
-	/* draw LOCK */
+	/* draw AUTOSNAP */
 	xco+= 8;
+	
+	uiDefIconTextButS(block, ICONTEXTROW,B_REDR, ICON_PROP_OFF, 
+						"Auto-Snap Keys %t|Off %x0|Frame Step %x1|Nearest Frame %x2", 
+						xco,0,XIC+10,YIC, &(G.saction->autosnap), 0, 1, 0, 0, 
+						"Auto-snapping mode for keys when transforming");
+	
+	xco+= (XIC + 18);
+	
+	/* draw LOCK*/
+		
 	uiDefIconButS(block, ICONTOG, 1, ICON_UNLOCKED,	xco, 0, XIC, YIC, 
 				  &(G.saction->lock), 0, 0, 0, 0, 
 				  "Updates other affected window spaces automatically "
 				  "to reflect changes in real time");
 
-
 	/* always as last  */
 	curarea->headbutlen = xco + 2*XIC;