MIPS R6 introduced new behavior for handling of NaN values
for TRUNC, FLOOR, CEIL and CVT instructions. Adding support for
the new behavior in MIPS and MIPS64 simulators. Fixing tests
for MIPS and MIPS64 to align them with the new behavior.

BUG=

Review URL: https://codereview.chromium.org/1488613007

Cr-Commit-Position: refs/heads/master@{#32499}