CLEANUP: channel: usr CF_/CHN_ prefixes instead of BF_/BUF_

Get rid of these confusing BF_* flags. Now channel naming should clearly
be used everywhere appropriate.

No code was changed, only a renaming was performed. The comments about
channel operations was updated.
diff --git a/src/proxy.c b/src/proxy.c
index 3568251..6e1f6e5 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -830,8 +830,8 @@
 	}
 
 	if (be->options2 & PR_O2_NODELAY) {
-		s->req->flags |= BF_NEVER_WAIT;
-		s->rep->flags |= BF_NEVER_WAIT;
+		s->req->flags |= CF_NEVER_WAIT;
+		s->rep->flags |= CF_NEVER_WAIT;
 	}
 
 	/* We want to enable the backend-specific analysers except those which