MEDIUM: log: add a new "raw" format

This format is pretty similar to the previous "short" format except
that it also removes the severity level. Thus only the raw message is
sent. This is suitable for use in containers, where only the raw
information is expected and where the severity is supposed to come
from the file descriptor used.
diff --git a/include/types/log.h b/include/types/log.h
index 3813cfb..d4d5976 100644
--- a/include/types/log.h
+++ b/include/types/log.h
@@ -42,6 +42,7 @@
 	LOG_FORMAT_RFC3164 = 0,
 	LOG_FORMAT_RFC5424,
 	LOG_FORMAT_SHORT,
+	LOG_FORMAT_RAW,
 	LOG_FORMATS,          /* number of supported log formats, must always be last */
 };