MINOR: channel: rename buffer_max_len() to channel_recv_limit()

Buffer_max_len() is ambiguous and misleading since it considers the
channel. The new name more accurately designates the size limit for
received data.
diff --git a/include/proto/channel.h b/include/proto/channel.h
index 1e786f3..15ff1a9 100644
--- a/include/proto/channel.h
+++ b/include/proto/channel.h
@@ -311,10 +311,10 @@
 }
 
 /* Return the max number of bytes the buffer can contain so that once all the
- * pending bytes are forwarded, the buffer still has global.tune.maxrewrite
+ * data in transit are forwarded, the buffer still has global.tune.maxrewrite
  * bytes free. The result sits between chn->size - maxrewrite and chn->size.
  */
-static inline int buffer_max_len(const struct channel *chn)
+static inline int channel_recv_limit(const struct channel *chn)
 {
 	return chn->buf->size - channel_reserved(chn);
 }
@@ -328,7 +328,7 @@
 {
 	int ret;
 
-	ret = buffer_max_len(chn) - chn->buf->i - chn->buf->o;
+	ret = channel_recv_limit(chn) - chn->buf->i - chn->buf->o;
 	if (ret < 0)
 		ret = 0;
 	return ret;
diff --git a/src/channel.c b/src/channel.c
index e9c5e12..177ab5a 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -157,7 +157,7 @@
 	if (unlikely(channel_input_closed(chn)))
 		return -2;
 
-	max = buffer_max_len(chn);
+	max = channel_recv_limit(chn);
 	if (unlikely(len > max - buffer_len(chn->buf))) {
 		/* we can't write this chunk right now because the buffer is
 		 * almost full or because the block is too large. Return the
diff --git a/src/payload.c b/src/payload.c
index fe9fdda..bc3dedd 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -213,8 +213,8 @@
 	 * all the part of the request which fits in a buffer is already
 	 * there.
 	 */
-	if (msg_len > buffer_max_len(s->req) + s->req->buf->data - s->req->buf->p)
-		msg_len = buffer_max_len(s->req) + s->req->buf->data - s->req->buf->p;
+	if (msg_len > channel_recv_limit(s->req) + s->req->buf->data - s->req->buf->p)
+		msg_len = channel_recv_limit(s->req) + s->req->buf->data - s->req->buf->p;
 
 	if (bleft < msg_len)
 		goto too_short;