add square cursors (for windows)

cursor icons squared with north-west gravity.
hotspots are identical to original icons.

otherwise gdkcursor-win32 creates square cursors with
center gravity and hotspot X/Y differs.

gtk2_ardour/icons/cursor_square/hotspots

@@ -0,0 +1,26 @@
+zoom_in_cursor 10 5
+zoom_out_cursor 5 5
+scissors 5 0
+grabber 5 0
+grabber_note 5 10
+grabber_edit_point 5 17
+trim_left_cursor 5 11
+anchored_trim_left_cursor 5 11
+trim_right_cursor 23 11
+anchored_trim_right_cursor 23 11
+trim_left_cursor_right_only 5 11
+trim_right_cursor_left_only 23 11
+fade_in_cursor 0 0
+fade_out_cursor 29 0
+resize_left_cursor 3 10
+resize_top_left_cursor 3 3
+resize_top_cursor 10 3
+resize_top_right_cursor 18 3
+resize_right_cursor 24 10
+resize_bottom_right_cursor 18 18
+resize_bottom_cursor 10 24
+resize_bottom_left_cursor 3 18
+move_cursor 11 11
+expand_left_right_cursor 11 4
+expand_up_down_cursor 4 11
+i_beam_cursor 4 11