srfi/74 always thinks the native endianness is big

[shawnw]

Looks like the reference implementation was just copied; the comment about changing the native endianness to match your platform is still present.

[shawnw]

Working version in Typed Racket at https://github.com/shawnw/racket-extra-srfi-libs/blob/master/typed/srfi/74.rkt ; feel free to steal it if desired.