[bgpgrep] Add human readable shorthand for attribute OTC (-attr option).

tools/bgpgrep/bgpgrep_compile.c

@@ -211,6 +211,7 @@ static BgpAttrCode ParseBgpAttr(void)
 	if (Df_stricmp(tok, "LARGE_COMMUNITY") == 0) return BGP_ATTR_LARGE_COMMUNITY;
 	if (Df_stricmp(tok, "BGPSEC_PATH") == 0) return BGP_ATTR_BGPSEC_PATH;
 	if (Df_stricmp(tok, "COMMUNITY_CONTAINER") == 0) return BGP_ATTR_COMMUNITY_CONTAINER;
+	if (Df_stricmp(tok, "OTC") == 0) return BGP_ATTR_OTC;
 	if (Df_stricmp(tok, "PREFIX_SID") == 0) return BGP_ATTR_PREFIX_SID;
 	if (Df_stricmp(tok, "SET") == 0) return BGP_ATTR_SET;