Make some internal namespace variable and argument names a bit friendlier to
C++ oriented editors and developer tools.

* subversion/libsvn_ra_serf/multistatus.c
  (global): Tweak comment.
  (multistatus_opened): Update user.

* subversion/libsvn_ra_serf/ra_serf.h
  (svn_ra_serf__dav_props_t,
   ns_t): Rename 'namespace' variables to 'xmlns'.

* subversion/libsvn_ra_serf/xml.c
  (define_namespaces,
   svn_ra_serf__expand_ns,
   svn_ra_serf__xml_cb_start,
   svn_ra_serf__xml_cb_cdata): Update caller.

* subversion/mod_dav_svn/dav_svn.h
  (dav_svn__new_error_tag): Rename argument.

* subversion/mod_dav_svn/util.c
  (dav_svn__new_error_tag): Rename argument.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1553809 13f79535-47bb-0310-9956-ffa450edef68