extract a couple constants to macros. discard unused macros

mouse_movement.cpp

@@ -37,8 +37,8 @@ void _warp_jump(long left, long top, long height, long width) {
 void begin_warping() {
     section_left = abs_left;
     section_top = abs_top;
-    next_width = 32767;
-    next_height = 32767;
+    next_width = MAX_WARP_WIDTH;
+    next_height = MAX_WARP_HEIGHT;
     is_warping = true;
 }
 

mouse_movement.h

@@ -16,8 +16,8 @@ void warp_mouse(Key key);
 // apparently, the mac discards 15% of the value space for mouse movement.
 // need to test this on other platforms
 
-#define HALF_WIDTH 16384
-#define HALF_HEIGHT 16384
+#define MAX_WARP_WIDTH 32767
+#define MAX_WARP_HEIGHT 32767
 
 
 // Mouse acceleration