Clarify Forsyth's and 9front's copyrights

I'm very grateful to Charles Forsyth for creating most of Jehanne's kernel
and to 9front's guys for all the code and ideas they freely share.

Here I make their copyrights explicit as they had been erroneusly omitted
or messed up before. Sorry.

sys/include/memdraw.h

@@ -6,6 +6,10 @@
  * modified, propagated, or distributed except according to the terms contained
  * in the LICENSE file.
  */
+/* Portions of this file are Copyright (C) 9front's team.
+ * See /doc/license/9front-mit for details about the licensing.
+ * See http://code.9front.org/hg/plan9front/ for a list of authors.
+ */
 
 #pragma	src	"/sys/src/lib/memdraw"
 #pragma	lib	"libmemdraw.a"
@@ -202,4 +206,3 @@ extern int		drawdebug;
 #pragma varargck type "lb" ulong
 #pragma varargck type "b" int
 #pragma varargck type "b" uint32_t
-