Tweaked the debug building and printing a little - I hope this works OK for everyone. Let me know if not.

Tamped down a few warnings.
For the demo/server Makefile, made an either/or choice between executable size optimization (normal) or gdb debug info and no optimization.

bacnet-stack/src/debug.c

@@ -55,4 +55,10 @@ void debug_printf(
 
     return;
 }
+#else
+void debug_printf(
+    const char *format,
+    ...) {
+    format = format;
+}
 #endif