patch 8.0.0925: MS-Windows GUI: channel I/O not handled right away

Problem:    MS-Windows GUI: channel I/O not handled right away.
Solution:   Don't call process_message() unless a message is available.
            (Yasuhiro Matsumoto, closes #1969)
diff --git a/src/version.c b/src/version.c
index ec75b71..67e96e6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    925,
+/**/
     924,
 /**/
     923,