[GEN][ZH] Fix game halting when left Alt key is pressed

[Mauller]

This PR prevents the game from freezing when the left ALT key is pressed.

The underlying issue is due to the games window process not acknowledging the WM_SYSCOMMAND SC_KEYMENU message.

Due to this, the message is then processed by the default window process which then will try to open the windows context menu which does not exist in this instance but causes the message loop to freeze.

• Resolves: Pressing ALT key in Windowed Mode stops the game update #105

This may also help prevent some mismatches that could be caused by a game freezing for too long when someone is playing in window mode.

[xezon]

I think the way it should be fixed is like so:

            switch( wParam )
            {
                case SC_MOVE:
                case SC_SIZE:
                case SC_MAXIMIZE:
                case SC_MONITORPOWER:
                  if( FALSE == ApplicationIsWindowed )
                    return 1;
                  break;
                case SC_KEYMENU:
                  return 1;
            }

[Mauller]

I think the way it should be fixed is like so:

            switch( wParam )
            {
                case SC_MOVE:
                case SC_SIZE:
                case SC_MAXIMIZE:
                case SC_MONITORPOWER:
                  if( FALSE == ApplicationIsWindowed )
                    return 1;
                  break;
                case SC_KEYMENU:
                  return 1;
            }

Did something similar to this but i stuck the SC_KEYMENU option first in the switch.

[Mauller]

Tweaked based on requests and also matched the indentation to match the surrounding code block.