Default double (pixel) screen size

OZvm is still by default rendering the "small" original 640x64 pixel screen by default, then re-drawn by ozvm.ini settings to double size.

This sometimes creates problems where occasionally the double screen is rendered inside the original 640x64 pixel screen. Only solution is to press F4 a few times for OZvm to get it right. Fix this problem by defaulting to double size by default!

Also, alternative resolutions are not picked up correctly from ini settings, ie. 640x320 is read, but screen is not resized to respect it.