release version 9.0

Problem:    About time to release Vim 9.0.
Solution:   Update the version number everywhere.
diff --git a/nsis/gvim_version.nsh b/nsis/gvim_version.nsh
index 92a7786..d8639a6 100644
--- a/nsis/gvim_version.nsh
+++ b/nsis/gvim_version.nsh
@@ -1,6 +1,6 @@
 # Generated from Makefile: define the version numbers
 !ifndef __GVIM_VER__NSH__
 !define __GVIM_VER__NSH__
-!define VER_MAJOR 8
-!define VER_MINOR 2
+!define VER_MAJOR 9
+!define VER_MINOR 0
 !endif