Per #24: plug gray streams protocol hole for CCL's benefit

Contrary to SBCL and Allegro, CCL calls STREAM-LINE-COLUMN on Fiasco's
special column-counting stream, but until now we didn't have an
implementation for it.  This broke tests on CCL for packages based
on Fiasco in certain pretty-printing situations.

* src/streams.lisp (trivial-gray-streams:stream-line-column):
New method.

* test/basic.lisp (slightly-verbose-test)
(slightly-verbose-test-2): New self tests.

src/streams.lisp

@@ -14,6 +14,11 @@
       (setf (output-column s) (- (length seq) newline-pos 1))))
   (write-sequence seq (slot-value s 'understream) :start start :end end))
 
+(defmethod trivial-gray-streams:stream-line-column
+    ((s column-counting-output-stream))
+  "Tell column number that stream S is currently at."
+  (output-column s))
+
 (defmethod trivial-gray-streams:stream-start-line-p
     ((s column-counting-output-stream))
   "Tell if stream S is already at start of fresh new line."

test/basic.lisp

@@ -139,6 +139,14 @@
       ))
   (values))
 
+(deftest slightly-verbose-test ()
+  (format *error-output* "~&Watch out for me")
+  (is t))
+
+(deftest slightly-verbose-test-2 ()
+  (format *error-output* "...And me")
+  (is t))
+
 (deftest lambda-list-processing ()
   (is (equal (lambda-list-to-value-list-expression '(p1 p2 &optional o1 (o2 "o2") &key k1 (k2 "k2") &allow-other-keys))
              '(list (cons 'p1 p1) (cons 'p2 p2) (cons 'o1 o1) (cons 'o2 o2) (cons 'k1 k1)