Chunk - Add the SA2B+ Specific NAT Strip Flag

[shaddatic]

SA2B added a new Chunk strip flag to disable alpha test in the material itself, rather than relying on a texture flag. There's no official name for it, since it's technically a user-flag in Ninja's eyes, but the name I've chosen is NAT/No Alpha Test; but I'm open to other ideas and want to hear other opinions on it.

It's only job is to disable Alpha Test/draw with full transparency, I have confirmed this. Here's the code snippet where it's used (modified to be more readable):

if ( (fst & NJD_FST_NAT)   || // IF NoAlphaTest flag on material
    bld_src == NJD_FBS_ONE || // OR src is ONE
    bld_dst == NJD_FBD_ONE || // OR dst is ONE
    TexHasNoAlphaTestFlag() ) // OR no alpha test tex flag
{
    SetTransparentDraw(); // No Alpha Test, full transparancy, no Z write
}
else
    SetAlphaTestDraw(); // Alpha Test and Z write

And here is the definition for it:

#define NJD_FST_NAT       (0x80<<8) // 0x8000

I originally wanted to remove it in Render Fix, but models genuinely use it so I will continue to support it. That, and it is actually quite useful to have.