BUG/MINOR: config: correctly report when log-format headers require HTTP mode

When using some log-format directives in header insertion without HTTP mode,
the config parser used to report a cryptic message about option httplog being
downgraded to tcplog and with "(null):0" as the file name and line number.

This is because the lfs_file and lfs_line were not properly set for some valid
use cases of log-format directives. Now we cover http-request and http-response
as well.
diff --git a/src/proxy.c b/src/proxy.c
index f0863d6..5458f1b 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -406,7 +406,7 @@
 	}
 	if (curproxy->to_log & (LW_REQ | LW_RESP)) {
 		curproxy->to_log &= ~(LW_REQ | LW_RESP);
-		Warning("parsing [%s:%d] : 'option httplog' not usable with %s '%s' (needs 'mode http'). Falling back to 'option tcplog'.\n",
+		Warning("parsing [%s:%d] : HTTP log/header format not usable with %s '%s' (needs 'mode http').\n",
 			curproxy->conf.lfs_file, curproxy->conf.lfs_line,
 			proxy_type_str(curproxy), curproxy->id);
 	}