Win32: Implement "-d" command-line switch, and update the DebugLog batch file accordingly.

This will make it so -d (which sets all of the logging levels to debug) works on Windows, too. Previously, it didn't do anything. Also, I updated the bat file so it'll work with the new option, and close itself after launching the emulator (via the "start" command), and not linger around.

Fixes https://github.com/hrydgard/ppsspp/issues/5773.