Support or explicitly reject older MCL #16
Description
On a lark, I tried to load Quicklisp on MCL 5.2 on an iBook G4 running Mac OS X 10.4.11. It failed because on that platform, there’s no CCL:make-socket to re-export from qlqs-ccl.
It’d be awesome if Quicklisp could support old versions of MCL, of course, but in the absence of support it should probably explicitly reject them.