We currently define our own _sunos, __freebsd, and __openbsd_ defines when building on Solaris, FreeBSD, and OpenBSD, respectively.

This is unnecessary, as there are already well defined preprocessor definitions for those platforms:

http://nadeausoftware.com/articles/2012/01/c_c_tip_how_use_compiler_predefined_macros_detect_operating_system#Solaris

We should standardize on the standard ones.