Merge revisions 1515049,-88,-6315,-6322,-6665 from "log addressing"
branch intro /trunk and resolve trivial text conflicts.

This patch generalizes the svn_checksum API implementation and
introduces support for FNV-1a.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1546699 13f79535-47bb-0310-9956-ffa450edef68