patch 8.1.0992: a :normal command resets the reg_executing() result

Problem:    A :normal command while executing a register resets the
            reg_executing() result.
Solution:   Save and restore reg_executing. (closes #4066)

src/version.c

@@ -779,6 +779,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    992,
 /**/
     991,
 /**/