Handle MySQL FK column names idenfier case, fix #62.

The code forgot completely that MySQL column name references in foreign
key definitions have to follow the identifier case rules, this patch fix
that.

To be able to do that, we need to parse the GROUP_CONCAT() result that
lists the FK columns, as there's apparently no arrays in MySQL. The
problem here is that about any character is allowed in column names when
`quoted`, so using a comma here might reveal to be fragile later.

src/pgsql/schema.lisp

@@ -75,15 +75,23 @@
 	  (apply-identifier-case (pgsql-fkey-name fk) identifier-case))
 	 (table-name
 	  (apply-identifier-case (pgsql-fkey-table-name fk) identifier-case))
+         (fkey-columns
+          (mapcar (lambda (column-name)
+                    (apply-identifier-case column-name identifier-case))
+                  (pgsql-fkey-columns fk)))
 	 (foreign-table
-	  (apply-identifier-case (pgsql-fkey-foreign-table fk) identifier-case)))
+	  (apply-identifier-case (pgsql-fkey-foreign-table fk) identifier-case))
+         (foreign-columns
+          (mapcar (lambda (column-name)
+                    (apply-identifier-case column-name identifier-case))
+                  (pgsql-fkey-foreign-columns fk))))
     (format nil
-	    "ALTER TABLE ~a ADD CONSTRAINT ~a FOREIGN KEY(~a) REFERENCES ~a(~a)"
+	    "ALTER TABLE ~a ADD CONSTRAINT ~a FOREIGN KEY(~{~a~^,~}) REFERENCES ~a(~{~a~^,~})"
 	    table-name
 	    constraint-name
-	    (pgsql-fkey-columns fk)
+	    fkey-columns
 	    foreign-table
-	    (pgsql-fkey-foreign-columns fk))))
+	    foreign-columns)))
 
 (defmethod format-pgsql-drop-fkey ((fk pgsql-fkey)
 				   &key all-pgsql-fkeys identifier-case)

src/sources/mysql-schema.lisp

@@ -261,11 +261,12 @@ GROUP BY table_name, index_name;" dbname))
 
  GROUP BY table_name, constraint_name, ft;" dbname dbname))
      do (let ((entry (assoc table-name schema :test 'equal))
-              (fk    (make-pgsql-fkey :name name
-                                      :table-name table-name
-                                      :columns cols
-                                      :foreign-table ftable
-                                      :foreign-columns fcols)))
+              (fk
+               (make-pgsql-fkey :name name
+                                :table-name table-name
+                                :columns (sq:split-sequence #\, cols)
+                                :foreign-table ftable
+                                :foreign-columns (sq:split-sequence #\, fcols))))
           (if entry
               (push fk (cdr entry))
               (push (cons table-name (list fk)) schema)))