Fall back to Fink's cvs if /usr/bin/cvs is missing.
Hey, let's actually have this work.
Check that the vcs executable is a file and then check that it's executable, to avoid pathologies like a "cvs" directory.
We don't need the full multiline results from querying the Xcode CLI receipt.
(finally) fix processing of Oracle's Java for 10.7 and later.

Note:  a side effect of the refactoring is that system-java16 disappears on 10.5/i386, since the Java-1.6 for that platform was distributed as x86_64 only, unlike on 10.6+.
Remove debugging output.