patch 8.0.0750: OpenPTY missing in non-GUI build

Problem:    OpenPTY missing in non-GUI build.
Solution:   Always include pty.c, add an #ifdef to skip over the contents.
diff --git a/src/version.c b/src/version.c
index 486cd6f..78a552d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    750,
+/**/
     749,
 /**/
     748,