Add an internal text conflict merge tool to the 'svn' command line client.
The merge tool's interface was inspired by the UNIX tool sdiff ("side-by-side diff"), which is used to merge configuration files during upgrades on OpenBSD, for example.
The merge tool can be invoked during interactive conflict resolution using the new "(m) merge" option. It is currently limited to picking either version of each conflicted chunk. It can also postpone resolution of a chunk, which will result in conflict markers in the merge result and the inability to mark the entire file as "(r) resolved".
The merge tool will be extended later with per-conflict-chunk editing capabilities which will make it more flexible than it is now.