Assorted fixes: catalogs SQLtypes and MySQL decoding as.

It turns out that when trying to debug "decoding as" the SQLtype listing
support in sqltype-list was found broken, so this patch fixes it. Then goes
on to fix the DECODING AS filters support, which we have switched to using
the better regexp-or-string filter struct but forgot to update the matching
code accordingly.

Fixes #665.

src/sources/mysql/mysql.lisp

@@ -235,13 +235,7 @@ Illegal ~a character starting at position ~a~@[: ~a~].~%"
 (defun apply-decoding-as-filters (table-name filters)
   "Return a generialized boolean which is non-nil only if TABLE-NAME matches
    one of the FILTERS."
-  (flet ((apply-filter (filter)
-           ;; we close over table-name here.
-           (typecase filter
-             (string (string-equal filter table-name))
-             (list   (destructuring-bind (type val) filter
-                       (ecase type
-                         (:regex (cl-ppcre:scan val table-name))))))))
+  (flet ((apply-filter (filter) (matches filter table-name)))
     (some #'apply-filter filters)))
 
 (defmethod instanciate-table-copy-object ((copy copy-mysql) (table table))

src/utils/catalog.lisp

@@ -204,7 +204,7 @@
 
 (defmethod sqltype-list ((table table) &key)
   "Return the list of sqltypes for SCHEMA."
-  (apply #'append (mapcar #'sqltype-list (table-column-list table))))
+  (mapcar #'sqltype-list (table-column-list table)))
 
 (defmethod sqltype-list ((schema schema) &key)
   "Return the list of sqltypes for SCHEMA."
@@ -215,7 +215,9 @@
 (defmethod sqltype-list ((catalog catalog) &key)
   "Return the list of sqltypes for CATALOG."
   (remove-duplicates
-   (apply #'append (mapcar #'sqltype-list (catalog-schema-list catalog)))
+   (remove-if #'null
+              (apply #'append
+                     (mapcar #'sqltype-list (catalog-schema-list catalog))))
    :test #'string-equal :key #'sqltype-name))
 
 (defmethod table-list ((schema schema) &key)