patch 8.1.0234: incorrect reference counting in Perl interface

Problem:    Incorrect reference counting in Perl interface.
Solution:   Call SvREFCNT_inc more often, add a test. (Damien)

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    234,
 /**/
     233,
 /**/