v.fmt: add an independent Comment.is_inline flag. Use it for fixing [ .. //x ] => [ .. //x, ]

vlib/net/http/cookie_test.v

@@ -443,7 +443,7 @@ const (
 			},
 			]
 		}
-		// TODO(bradfitz): users have reported seeing this in the,,
+		// TODO(bradfitz): users have reported seeing this in the
 		// wild, but do browsers handle it? RFC 6265 just says "don't
 		// do that" (section 3) and then never mentions header folding
 		// again.