Using sidec03.mix for Yuri's GUI

To make the game load the "sidec03.mix" file for Yuri's GUI, simply add the following tag to the [General] section:

LoadSpecialYuriUI=yes

Note that firstly, the MIX file must exist in order to play a game as Yuri, secondly, some filenames must be different than usual:

bkgdlgy.shp instead of bkgdlg.shp
bkgdmdy.shp instead of bkgdmd.shp
bkgdsmy.shp instead of bkgdsm.shp
radary.shp instead of radar.shp
uibkgdy.pal instead of uibkgd.pal (for bkgdsmy.shp, bkgdmdy.shp and bkgdlgy.shp)
radaryuri.pal instead of sidebar.pal (for radary.shp)