+(Why doesn't SBCL support more extensions? Why the hell did I (WHN)
+drop all those nice extensions from CMU CL when the code already
+exists? This is a frequently asked question on the mailing list. The
+answer is that they're hard to maintain, and I have enough on my hands
+already. Also, in the case of some big and unquestionably useful
+extensions, like sockets and Motif, I think that SBCL has done its job
+by supplying the FFI, and that people who need, and understand, and
+are motivated to maintain the functionality should supply it as a
+separate library, which I'd be happy to distribute or link to on the
+SBCL home page. Finally, in the case of multithreading, I do think it
+belongs in the new ANSI spec, and it'd be a good feature to have, but
+I didn't think the CMU CL implementation was sufficiently mature, and
+it's such a complicated and far-reaching extension that I thought that
+trying to fix it would interfere with the more urgent task of getting
+basic ANSI support up to speed.)
+