Address huf / piz performance regressions (AcademySoftwareFoundation#…

…1868)

* Enable fast huf for os/x, optimize routines

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>

* Apply some minor optimizations to piz decode

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>

* disable alias tag for msvc

It appears MSVC does not handle the restrict keyword properly

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>

* Replicate comment denoting issue w/ msvc

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>

* Remove overzealous memory optimization

It is more efficient to store the code length and symbol in the one
table, but appears measurably slower. Remove that.

Further, do not constantly refill the bit buffer during huf fast decode,
that slows down the decoding

Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>

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Signed-off-by: Kimball Thurston <kdt3rd@gmail.com>