patch 8.2.0388: printmbcharset option not tested

Problem:    Printmbcharset option not tested.
Solution:   Add a test.  Enable PostScript for AppVeyor build. (Dominique
            Pelle, closes #5783)
diff --git a/src/version.c b/src/version.c
index a25685c..3724b9b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    388,
+/**/
     387,
 /**/
     386,