Applying FOV gun scaling for the triangle renderer as well

[Diordany]

Issue

The FOV gun scaling wasn't applied to the triangle renderer (with r_showtris = 1), resulting in geometry that differs from the output of the regular renderer:

Patch

I copied the scaling procedure to the triangle renderer which makes them match now:

The scaling procedure was copied from R_DrawAliasModel() into R_DrawAliasModel_ShowTris.

[sezero]

@andrei-drexler , @ericwa : This looks good?

[sezero]

OK, I pulled this in. Thanks.