location: Start column numbers at 1.

* guix/utils.scm (source-properties->location): Use COL + 1.

guix/utils.scm

@@ -662,4 +662,5 @@ (define (source-properties->location loc)
   (let ((file (assq-ref loc 'filename))
         (line (assq-ref loc 'line))
         (col  (assq-ref loc 'column)))
-    (location file (and line (+ line 1)) col)))
+    ;; In accordance with the GCS, start line and column numbers at 1.
+    (location file (and line (+ line 1)) (and col (+ col 1)))))