main: zero initialize opts

Without zero initialization, anything can be in the "Opts" struct when the program is started. On asus-me176c this causes osk-sdl to always run in test mode (480x800 centered on the screen, but touch screen fills full screen...).

Screenshot Before (click me)

Screenshot After (click me)

Possibly related: #90 (closed)

src/main.cpp

@@ -45,7 +45,7 @@ static string ErrorText = "Incorrect passphrase";
 
 int main(int argc, char **args) {
   list<string> passphrase;
-  Opts opts;
+  Opts opts{};
   Config config;
   SDL_Event event;
   SDL_Window *display = NULL;