UserspaceEmulator: Use a report() function instead of dbgprintf()

Ultimately we'll want to make it a bit easier to add more reporting.
This at least makes it easier to redirect the logging.

DevTools/UserspaceEmulator/Emulator.h

@@ -140,4 +140,6 @@ private:
     FlatPtr m_free_symbol_end { 0 };
 };
 
+void report(const char*, ...);
+
 }