move: Warp: move pointer to centre of window

When a user issues a Move command, such as:

    Move -10p -10p Warp

The mouse pointer would move to the window's same resting place
coordinate, rather than to the window itself.

This appears to have been broken in fvwm2 for some time.

Rather than reimplement the logic found in WarpToWindow, let "Warp"
imply warping the pointer to the centre of the window.

Eventually, "Warp" as an option will go away entirely, so this is only
meant as a temporary solution as it's technically something which we
support.

Should the user want anything more granular or a different pointer
location than what "Warp" now implies with this comment, then the
"WarpToWindow" command can be used instead.

Fixes #551

fvwm/move_resize.c

@@ -1903,9 +1903,8 @@ static void __move_window(F_CMD_ARGS, Bool do_animate, int mode)
 			fw->g.frame.height, True);
 		if (fWarp & !do_animate)
 		{
-			FWarpPointer(
-				dpy, None, None, 0, 0, 0, 0, FinalX - x,
-				FinalY - y);
+			char *cmd = "WarpToWindow 50 50";
+			execute_function_override_window(NULL, exc, cmd, 0, fw);
 		}
 		if (IS_MAXIMIZED(fw))
 		{
@@ -2169,7 +2168,7 @@ static void DoSnapAttract(
 			/* horizontally */
 			if (!(*py + self.height < mon_y || *py > mon_y + mon_h))
 			{
-				if (*px + self.width >= 
+				if (*px + self.width >=
 					mon_w + mon_x - fw->snap_attraction.proximity &&
 					*px + self.width <=
 					mon_w + mon_x + fw->snap_attraction.proximity)