x11-wm/stumpwm: re-add after deletion in 2014

Instead of bundling StumpWM, SBCL, and other libraries into one large
executable, pull in SBCL and the other dependencies and use the simple CL
framework that other FreeBSD CL ports use.

Since StumpWM only supports running under SBCL, the port pulls in the
*-sbcl port dependencies and conforms to the framework itself, except that
it directly installs the fasl files instead of having an associated
x11-wm/stumpwm-sbcl. This means no fasl files will be generated under
~/.cache/common-lisp/sbcl-*/ [1] and the package is only made up of the
source, fasl files, and a few small, miscellaneous files. From a user
perspective, they still get an executable, but it is a small shell script
and the package is under 3 MB instead of around 65 MB.

[1] Loading personal modules in ~/.stumpwmrc will still generate fasl files

under ~/.cache/common-lisp/sbcl-*/