Update code style

Limit source code to 80 chars, and declare functions return type and
modifiers on a separate line.

This allows to avoid very long lines, and all function names are
aligned.

(We do this on VLC, and I like it.)

app/src/scrcpy.h

@@ -18,6 +18,7 @@ struct scrcpy_options {
     SDL_bool no_window;
 };
 
-SDL_bool scrcpy(const struct scrcpy_options *options);
+SDL_bool
+scrcpy(const struct scrcpy_options *options);
 
 #endif