switch to libosmocore multihread-logging

When osmo-remsim was originally developed, libosmocore logging was
not yet thread-safe.  This meant that the worker threads of remsim-bankd
and remsim-server could not log via the libosmocore logging framework
but directly used stderr/stdout, which produced rather inconsistent log
output.

However, since 1.3.0, libosmocore has received support for
multi-threaded applications.  Let's make use of this and consistently
use it in remsim-server and remsim-bankd.  This obviously also means
adding some more log categories.

Change-Id: I7bd5264c559b756927046563a2d00c54826bee9b
diff --git a/src/debug.h b/src/debug.h
index 51331f4..88288ca 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -5,6 +5,9 @@
 	DMAIN,
 	DST2,
 	DRSPRO,
+	DREST,
+	DSLOTMAP,
+	DBANKDW,
 };
 
 extern const struct log_info log_info;