VSL manual polish

We should avoid the word "received" in the context of response fields,
since we don't "receive" resp.* fields, only beresp. This also fixes
another inconsistency in the manual:

    RespReason - Client response response
        The HTTP response string received.

include/tbl/vsl_tags_http.h

@@ -58,11 +58,11 @@ SLTH(Protocol,	HTTP_HDR_PROTO,		1, 1, "protocol",
 )
 
 SLTH(Status,	HTTP_HDR_STATUS,	0, 1, "status",
-	"The HTTP status code received.\n\n"
+	"The HTTP response status code.\n\n"
 )
 
-SLTH(Reason,	HTTP_HDR_REASON,	0, 1, "response",
-	"The HTTP response string received.\n\n"
+SLTH(Reason,	HTTP_HDR_REASON,	0, 1, "reason",
+	"The HTTP response reason string.\n\n"
 )
 
 SLTH(Header,	HTTP_HDR_FIRST,		1, 1, "header",