Speed up sending proplists via ra_svn by explicitly sending the elements
of the property tuples instead of using the generic write_tuple code.
Also, eliminate a mostly unused sub-pool.

* subversion/libsvn_ra_svn/marshal.c
  (svn_ra_svn__write_proplist): shorten and optimize


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1486008 13f79535-47bb-0310-9956-ffa450edef68