Patches from Walter C. Pelissero on clsql mail list

- db-postgresql.lisp, sql/fddl.lisp: Fix typos
- sql/metaclasses.lisp: Work around type-check-function being set
  during defclass expansion in SBCL
- uffi/clsql-uffi.lisp: In call to uffi:convert-from-foreign-string,
  Set null-terminated-p to T when length not specified.