patch 8.0.0751: OpenPTY missing with some combination of features

Problem:    OpenPTY missing with some combination of features. (Kazunobu
            Kuriyama)
Solution:   Adjust #ifdef.  Also include pty.pro when needed.
diff --git a/src/version.c b/src/version.c
index 78a552d..174fc0d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    751,
+/**/
     750,
 /**/
     749,