test: make test-smalloc endian aware

The test/simple/test-smalloc.js has an implicit assumption
of the byte order of the data stored for Double and Uint32
values. On a big endian platform this test fails without
these patches.

Use os.endianness() to detect the endian of the platform
and use it to gate the static value used for comparison.
Merge remote-tracking branch 'upstream/master'