patch 8.1.0363: internal diff isn't used by default as advertised

Problem:    Internal diff isn't used by default as advertised.
Solution:   Add "internal" to the default value of 'diffopt'.
            Also add couple of files missing from the distribution.

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    363,
 /**/
     362,
 /**/