MIPS: Add NaN test to cctest/test-macro-assembler-mips.

NaN value is different on MIPS and x86 architectures, and TEST(NaNx)
tests checks the case where a x86 NaN value is serialized into the snapshot
on the simulator during cross compilation.

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/144473008

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19241 ce2b1a6d-e550-0410-aec6-3dcde31c8c00