Maybe-inline float accessors ieee-{single,double}-{set,ref}/{le,be}

At least in SBCL on x86_64, the inlined version is several times faster
and the code size is comparable to full calls with spilling that would
be used otherwise.
Merge pull request #16 from scymtym/master

Maybe-inline float accessors ieee-{single,double}-{set,ref}/{le,be}