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

Many parts of the channel definition still make use of the "buffer" word.
diff --git a/Makefile.bsd b/Makefile.bsd
index 9fc9b61..ca00c7b 100644
--- a/Makefile.bsd
+++ b/Makefile.bsd
@@ -106,7 +106,8 @@
 LDFLAGS = -g
 
 OBJS = src/haproxy.o src/sessionhash.o src/base64.o src/protocols.o \
-       src/uri_auth.o src/standard.o src/buffers.o src/log.o src/task.o \
+       src/uri_auth.o src/standard.o src/buffer.o src/log.o src/task.o \
+       src/chunk.o src/channel.o \
        src/time.o src/fd.o src/pipe.o src/regex.o src/cfgparse.o src/server.o \
        src/checks.o src/queue.o src/frontend.o src/proxy.o src/proto_uxst.o \
        src/proto_http.o src/raw_sock.o src/appsession.o src/backend.o \