patch 8.1.2304: cannot get the mouse position when getting a mouse click

Problem:    Cannot get the mouse position when getting a mouse click.
Solution:   Add getmousepos().
diff --git a/src/version.c b/src/version.c
index 5d97575..b08106c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2304,
+/**/
     2303,
 /**/
     2302,