Apparently mingw/gcc is too stupid to recognise that the values
in alphatest will only be used if they're within the range of
unsigned char (i.e. 0 <= x < 255) when this is done using a ternary
operator. Then again, it's quite hard for humans to immediately
parse what is going on here either! Converting this clever code
back to a more obvious form that mere mortals (and compilers it
seems) can handle with ease ;)
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