update buildnumber to fit the current svn revision

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@926 14438d79-0ffd-4333-8ae7-ea2bdd901387
better set build number to version number 921 = 9.2.1

git-svn-id: svn://svn.code.sf.net/p/vpinball/code/trunk@927 14438d79-0ffd-4333-8ae7-ea2bdd901387