Import the new logging architecture

This is the new logging architecture, including

* support for multiuple logging targets like stderr and vty
* log levels in addition to categories/subsystems
* filtering based on imsi, i.e. only see events for one subscriber
* dynamically change log level for each category for each vty
diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index 787a803..d669ba0 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -237,6 +237,8 @@
 	}
 
 	lchan = &ts->lchan[lch_idx];
+	debug_set_context(BSC_CTX_LCHAN, lchan);
+	debug_set_context(BSC_CTX_SUBSCR, lchan->subscr);
 
 	return lchan;
 }