remove dependence on pool library.

Reference: /n/sources/patch/applied/layer-no-pool
Date: Wed Oct 10 16:04:32 CES 2012
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libmemlayer/draw.c	Wed Oct 10 16:03:22 2012
+++ /sys/src/libmemlayer/draw.c	Wed Oct 10 16:03:21 2012
@@ -3,7 +3,6 @@
 #include <draw.h>
 #include <memdraw.h>
 #include <memlayer.h>
-#include <pool.h>
 
 struct Draw
 {
--- /sys/src/libmemlayer/lhide.c	Wed Oct 10 16:03:23 2012
+++ /sys/src/libmemlayer/lhide.c	Wed Oct 10 16:03:23 2012
@@ -3,7 +3,6 @@
 #include <draw.h>
 #include <memdraw.h>
 #include <memlayer.h>
-#include <pool.h>
 
 /*
  * Hide puts that portion of screenr now on the screen into the window's save area.
--- /sys/src/libmemlayer/ltofront.c	Wed Oct 10 16:03:24 2012
+++ /sys/src/libmemlayer/ltofront.c	Wed Oct 10 16:03:24 2012
@@ -3,7 +3,6 @@
 #include <draw.h>
 #include <memdraw.h>
 #include <memlayer.h>
-#include <pool.h>
 
 /*
  * Pull i towards top of screen, just behind front