dissolve libcommon: drop debug.c

Apply more concise logging categories in each main scope. The bulk goes to
msc_main.c, obviously, while tests and utils get a slimmed down bunch of
logging categories.

Change-Id: I969a0662ba273f3721b6820d02151b7a5b8014b8
diff --git a/src/libcommon/oap_client.c b/src/libcommon/oap_client.c
index 7154baa..137515a 100644
--- a/src/libcommon/oap_client.c
+++ b/src/libcommon/oap_client.c
@@ -24,6 +24,7 @@
 #include <errno.h>
 
 #include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
 #include <osmocom/crypt/auth.h>
 #include <osmocom/gsm/oap.h>