patch 8.1.1810: popup_getoptions() is missing an entry for "mapping"

Problem:    Popup_getoptions() is missing an entry for "mapping".
Solution:   Add the entry.
diff --git a/src/version.c b/src/version.c
index 83c11ab..6904482 100644
--- a/src/version.c
+++ b/src/version.c
@@ -774,6 +774,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1810,
+/**/
     1809,
 /**/
     1808,