Add popular common lisp implementations

1) Return clisp to the ports collection. clisp was removed from FreeBSD and DragonFlyBSD recently for god knows why. It's still one of the most popular CL implementations with support of ANSI CL standard, multithreading and so on.

2) Add SBCL port. SBCL is the most advanced and fast open source CL implementation, supporting native code compilation, having many extensions etc. It was recently ported to DragonFlyBSD. Needs clisp for compilation (because about 90% of it is written in common lisp). Multithreading doesn't work on DragonFlyBSD, so it is switched off in the port.

Please set MAINTAINER to whatever you need. Surely, I will watch these ports in future, but I don't know to what exactly this variable is usually set to.

    wbr, Vasily Postnicov