release version 9.0

Problem:    About time to release Vim 9.0.
Solution:   Update the version number everywhere.
diff --git a/runtime/doc/pi_getscript.txt b/runtime/doc/pi_getscript.txt
index 980507d..87d4a4a 100644
--- a/runtime/doc/pi_getscript.txt
+++ b/runtime/doc/pi_getscript.txt
@@ -1,4 +1,4 @@
-*pi_getscript.txt*  For Vim version 8.2.  Last change: 2017 Aug 01
+*pi_getscript.txt*  For Vim version 9.0.  Last change: 2017 Aug 01
 >
 		GETSCRIPT REFERENCE MANUAL  by Charles E. Campbell
 <