Allow the compiler to micro-optimize byte swapping functions by evaluating them at compile time rather than at run time.  As for x86 and amd64, this requires GCC and it's enabled only if __OPTIMIZE__ is defined (ie, if at least -O is used).
Allow the compiler to micro-optimize byte swapping functions by
evaluating them at compile time rather than at run time.  As for x86
and amd64, this requires GCC and it's enabled only if __OPTIMIZE__ is
defined (ie, if at least -O is used).

Reviewed by:	jake

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