Allow building from either SVN or SVK

- create gnc-svnversion script that builds the revision number
  from either SVN or SVK.  The script should fail gracefully if
  you don't have SVK installed
- convert the configure script to use the new gnc-svnversion script
- convert the splash-screen Makefile to use the gnc-svnversions script

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@14427 57a11ea4-9604-0410-9ed3-97b8803252fd

Makefile.am

@@ -75,7 +75,8 @@ EXTRA_DIST = \
   po/glossary/zh_TW.po \
   intltool-extract.in \
   intltool-merge.in \
-  intltool-update.in
+  intltool-update.in \
+  util/gnc-svnversion
 
 bin_SCRIPTS = gnucash-config