In mod_dav_svn, reuse a single bucket brigade when responding to GET requests without an "X-SVN-VR-Base" header, i.e., without a delta base.
In mod_dav_svn, reuse a single bucket brigade when responding to GET
requests without an "X-SVN-VR-Base" header, i.e., without a delta base.

Previously we were creating a new brigade per every chunk of data, and
that caused an excessive memory usage of around 7-8 MB while serving a
800 MB-sized response.

This was pointed out by Joe Orton <jorton@redhat.com> as a part of the
discussion in http://svn.haxx.se/dev/archive-2016-08/0028.shtml

* subversion/mod_dav_svn/repos.c
  (deliver): Rewrite the code to reuse a single bucket brigade within the
   loop, and properly call apr_brigade_destroy() when the brigade is no
   longer required.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1757529 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion