Does not build - internal SBCL symbol reference

[quicklisp]

http://report.quicklisp.org/2020-02-27/failure-report/unicly.html#unicly has the full log.

[icer-p]

I can't access the report, but it's likely the issue resolved in my pull request #6.

I upgraded from an older SBCL provided by Ubuntu 20.04 to a SBCL 2.1.9 binary from the SBCL website. After the upgrade, my build of unicly broke with error:

; caught ERROR: ; READ error during COMPILE-FILE: ;
; Lock on package SB-IMPL violated when interning +MIN-HASH-TABLE-SIZE+ while ; in package UNICLY. ; See also: ; The SBCL Manual, Node "Package Locks" ;
; (in form starting at line: 148, column: 0, position: 7485)