Remove deprecated make-replay-repo script

The t10?-replay-* scripts now cover all the cases (and then some)
that the make-replay-repo script tried to cover.
Support caller-supplied wc_target path

Introduce a "--wc" command-line argument to svnreplay.py. The
immediate need is so that we can use "prove" with multiple jobs to
parallelize running the unit-tests.
Clean-up unit-tests

* Move to a stricter unit-test naming convention:
  * t1xxx-*.sh are the svnreplay tests.
  * t2xxx-*.sh are the svnancest tests.
* Support multi-jobbing unit-tests.  Make all the unit-tests
  multi-job safe, e.g. use unique repo's and wc's for each test.
* Ensure all test logic is run via assert's.
* Introduce "prove" Makefile target for unit-tests, to allow
  running all the tests multi-jobbed via prove.
Update links to http://nynim.org/code/svn2svn/

Renamed /projects/ -> /code/ on my personal site. Updating external
referencers.