[client] config: add new audio:micAlwaysAllow option

This will be used to always grant access to microphones instead of
prompting every time.

client/src/main.h

@@ -202,6 +202,7 @@ struct AppParams
 
   int               audioPeriodSize;
   int               audioBufferLatency;
+  bool              micAlwaysAllow;
 };
 
 struct CBRequest