Implement text cursor position protocol.

Here we create a new client/compositor interface in weston to allow
clients to report their x/y cursor position to the compositor. These
values are then used to center the zoom area on this point. This
is useful for everyone, especially people who are visually impaired.
diff --git a/src/shell.c b/src/shell.c
index e1f3a04..dc4fa47 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -1689,7 +1689,8 @@
 
 			weston_output_update_zoom(output,
 			                          seat->pointer->x,
-						  seat->pointer->y);
+						  seat->pointer->y,
+						  ZOOM_POINTER);
 		}
 	}
 }