updated for version 7.4.506

Problem:    MS-Windows: Cannot open a file with 259 characters.
Solution:   Fix off-by-one error. (Ken Takata)

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    506,
 /**/
     505,
 /**/