Converting floats to fixnums

[cartier@math.uqam.ca (Guillaume Cartier)]

Hello all MCL'ers,

  I am developing a software in which it is vital that I can
  convert a float into a fixnum in the fastest way possible and
  with no memory allocation.

  ROUND, FLOOR and company all return a second float value
  that I don't need and are relatively slow.

  Any idea? Internal undocumented stuff is ok with me...

PS: The method used to obtain the fixnum (i.e. rounding, flooring,
    truncating, ...) is not important.

Any answer will be well appreciated.

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