MINOR: opentracing: add ARGC_OT enum

Due to the addition of the OpenTracing filter it is necessary to define
ARGC_OT enum.  This value is used in the functions fmt_directive() and
smp_resolve_args().

include/haproxy/arg-t.h

@@ -82,6 +82,7 @@ enum {
 	ARGC_UBK,      /* use_backend message */
 	ARGC_USRV,     /* use-server message */
 	ARGC_HERR,     /* http-error */
+	ARGC_OT,       /* opentracing scope args */
 };
 
 /* flags used when compiling and executing regex */

src/log.c

@@ -284,6 +284,8 @@ static inline const char *fmt_directive(const struct proxy *curproxy)
 		return "use_backend";
 	case ARGC_HERR:
 		return "http-error";
+	case ARGC_OT:
+		return "ot-scope";
 	default:
 		return "undefined(please report this bug)"; /* must never happen */
 	}

src/sample.c

@@ -1136,6 +1136,7 @@ int smp_resolve_args(struct proxy *p)
 		case ARGC_SRV:   where = "in server directive in"; break;
 		case ARGC_SPOE:  where = "in spoe-message directive in"; break;
 		case ARGC_HERR:  where = "in http-error directive in"; break;
+		case ARGC_OT:    where = "in ot-scope directive in"; break;
 		}
 
 		/* set a few default settings */