REORG: buffers: split buffers into chunk,buffer,channel

Many parts of the channel definition still make use of the "buffer" word.
diff --git a/src/peers.c b/src/peers.c
index c293971..894502a 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -28,7 +28,7 @@
 #include <types/peers.h>
 
 #include <proto/acl.h>
-#include <proto/buffers.h>
+#include <proto/channel.h>
 #include <proto/fd.h>
 #include <proto/log.h>
 #include <proto/hdr_idx.h>