Fix some leaks/missed checks in the unit tests

Coverity spotted these.
Clarify ClientOnly documentation

The option is unneeded, not meaningless, so explain what it does.

Patch from Matt Pagan; fixes 9059.
Sort the 0.2.5.3-alpha changelog entries a little better.

Still haven't edited any.

Also, remove all the changes/* entries that got merged back in
6b5ef3889d83c715973d.
Update to latest tinytest

(This pulls in some fixes to tinytest_demo.c, which Tor doesn't build.)