release version 9.0

Problem:    About time to release Vim 9.0.
Solution:   Update the version number everywhere.
diff --git a/READMEdir/README_srcdos.txt b/READMEdir/README_srcdos.txt
index ca016bd..2bef9de 100644
--- a/READMEdir/README_srcdos.txt
+++ b/READMEdir/README_srcdos.txt
@@ -1,8 +1,8 @@
-README_srcdos.txt for version 8.2 of Vim: Vi IMproved.
+README_srcdos.txt for version 9.0 of Vim: Vi IMproved.
 
 See "README.txt" for general information about Vim.
 See "README_dos.txt" for installation instructions for MS-Windows.
-These files are in the runtime archive (vim82rt.zip).
+These files are in the runtime archive (vim90rt.zip).
 
 
 The DOS source archive contains the files needed to compile Vim on MS-Windows.