Fix an out-of-bounds read in the delta combiner.

* subversion/libsvn_delta/compose_delta.c (copy_source_ops):
   When initializing fix_limit, do not read past the end of the offsets array.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1569415 13f79535-47bb-0310-9956-ffa450edef68