Update documentation somewhat.

Indeed, at least on ABCL, the same binaries can run on either.
On other implementations, the same may or may not hold for FASLs.

Also, update testing infrastructure to work with latest xcl from git.

Fix documentation typo and update debian metadata.

Fix link in webpage (lp#614806).
Include SCL and ABCL in my testing routine.

Update debian configuration and documentation.