Increase screen resolution

[aserebryakov]

The current screen resolution is 320x200, that is quite low for modern PC.

It is needed to increase screen resolution.

[aserebryakov]

A new branch "sdl_doom_640x400" was created in order to increase screen resolution.

[aserebryakov]

In the commit 2e3d0f9 the initial support of 640x400 resolution was implemented.
There are several bugs present.

[aserebryakov]

In the commit 0132ac6 most of menus were placed on the center of the screen.
Exception: Episode, Read this.

[aserebryakov]

In the revision e7b46d0 status bar position was fixed.