Add peg revision parameter to new svn_repos_node_location_segments() API.
(This is the first of multiple commits whereby I have the pleasure of propogating this addition back through the corresponding RA APIs, fallback code, etc. Yay!)
* subversion/include/svn_repos.h (svn_repos_node_location_segments): Add a peg revision parameter.
* subversion/libsvn_repos/rev_hunt.c (maybe_crop_and_send_segment): New helper. (svn_repos_node_location_segments): Add and use a peg revision parameter.
* subversion/svnserve/serve.c, * subversion/libsvn_ra_local/ra_plugin.c, * subversion/mod_dav_svn/reports/get-location-segments.c Callers of svn_repos_node_location_segments() updated to pass peg revision (same as start revision for these invocations at the moment).
* subversion/tests/libsvn_repos/repos-test.c (check_location_segments): Add peg revision and end revision parameters. (node_location_segments): Add some tests that flex the new peg revision parameter.