Float indexes

[Chris Muller]

While working on the new query stuff I noticed that Float ranges
spanning 0.0 won't work properly.  That is, the hash values calculated
for negative floats (from #asIEEE32BitWord) are greater than those for
positive numbers.

  -3.0 asIEEE32BitWord < 3.0 asIEEE32BitWord    "false"

Probably no one is using it anyway but I thought it worth mentioning.

Apparently there are also some Mantis bugs open on these methods too.

  http://bugs.impara.de/view.php?id=3133