add bsn_log extension

This provides a mechanism for either the controller or switch to request the
other side to output a log message, subject to the configured loglevel. This is
useful for log (and OpenFlow pcap) correlation.
diff --git a/c_gen/templates/loci_show.h b/c_gen/templates/loci_show.h
index aff632f..2a1925d 100644
--- a/c_gen/templates/loci_show.h
+++ b/c_gen/templates/loci_show.h
@@ -412,5 +412,6 @@
 #define LOCI_SHOW_desc_str_image_checksum(write, cookie, val) LOCI_SHOW_desc_str(writer, cookie, val)
 #define LOCI_SHOW_desc_str_startup_config_checksum(write, cookie, val) LOCI_SHOW_desc_str(writer, cookie, val)
 #define LOCI_SHOW_u16_bsn_tcp_flags(write, cookie, val) LOCI_SHOW_x16(writer, cookie, val)
+#define LOCI_SHOW_u8_loglevel(writer, cookie, val) LOCI_SHOW_u8(writer, cookie, val)
 
 #endif /* _LOCI_SHOW_H_ */