Comment 1 for bug 1192929

Bisected (on x86-64, Linux) to:

cd5a858174d892f876699373dc3ea389cf2c4d40 is the first bad commit
commit cd5a858174d892f876699373dc3ea389cf2c4d40
Author: Stas Boukarev <email address hidden>
Date: Wed Jun 5 18:38:42 2013 +0400

Optimize (mod FIXNUM) type-checks on x86oids.

Instead of two (and (>= x 0) (< x FIXNUM)) comparisons, do one
unsigned.
(mod power-of-two) is further optimized by doing one mask test
determine the range and fixnumness in one go.