vchoi_fork

[svn-r8805] Purpose:
    Code optimization & bug fix

Description:
    Speed up "fast comparison" lookups in trees by a factor of 2-3x

    Correctly handle "fast comparisons" for unsigned values (esp. hsize_t).

Solution:
    Mostly removing if statements and redundant assigns, etc.

Platforms tested:
    Solaris 2.7 (arabica)
    FreeBSD 4.10 (sleipnir) w/parallel
    Too minor to require h5committest