Make gcc happy and remove a couple of warnings

Remove the callbacks from gsm_network for now. A set of different
callbacks will be back. E.g. when the paging is completed, when the
Q.931 like call handling is there...

Remove var's or move them into #if 0, remove unused stuff that looks
like we do not need it anytime soon or #if 0 them, move stuff around.
diff --git a/include/openbsc/debug.h b/include/openbsc/debug.h
index d30f0d0..5671980 100644
--- a/include/openbsc/debug.h
+++ b/include/openbsc/debug.h
@@ -22,6 +22,7 @@
 
 #define static_assert(exp, name) typedef int dummy##name [(exp) ? 1 : -1];
 
+void hexdump(unsigned char *buf, int len);
 void debugp(unsigned int subsys, char *file, int line, const char *format, ...);
 void debug_parse_category_mask(const char* mask);
 void debug_use_color(int use_color);