ra_serf: Teach get_file RA op to ask for compression if available.
ra_serf: Teach get_file RA op to ask for compression if available.

* subversion/libsvn_ra_serf/update.c
  (svn_ra_serf__get_file): Install header delegate to install gzip request
  header.

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