patch 8.2.3766: converting a funcref to a string leaves out "g:"

Problem:    Converting a funcref to a string leaves out "g:", causing the
            meaning of the name depending on the context.
Solution:   Prepend "g:" for a global function.

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3766,
 /**/
     3765,
 /**/