SQL parsing irregularity when using SQL reader syntax.

Platform: Postgres/Linux

Reproduction:

(let ((my-string (make-string 1 :initial-element #\Nul)))
   (select [foo] :from [bar] :where [= [foo] my-string]))

You should get an error about an unterminated string constant, caused by the nul
character eventually being treated as a C-string terminating nul. Discovered by
a hacker who was trying to SQL-inject me.