Add a few missing dependencies that caused errors when I tried to compile subversion libraries as dlls.
Add a few missing dependencies that caused errors when I tried to
compile subversion libraries as dlls.

* build.conf
  (libsvn_subr, svnversion, aprutil):
    add missing dependencies
    
  (xml):
    set "external-lib" option

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion