Make libfaketime build, run and pass tests on SmartOS.

Since SmartOS is close to SunOS, it's possible that these changes make
libfaketime build and run on other SunOS-like platforms.

These changes were tested on MacOS X and Ubuntu 12.04, and no regression
appeared during testing.
Merge pull request #50 from joyent/sunos-smartos-support

Make libfaketime build, run and pass tests on SmartOS.