When sending properties to the server, don't use the custom namespace if the property name already begins with "svn:".
When sending properties to the server, don't use the custom namespace if the
property name already begins with "svn:".

(do_setprop): test the name for "svn:" and use the right namespace prefix

(do_proppatch): define the "C" prefix for the custom namespace and use "S"
  for the normal "svn:" namespace. For deletes, use the correct prefix based
  on the property name.

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