illumos gate

Many unix-based distributions include a mechanism where the /etc/profile and /etc/.login initialization scripts source any initialization files in /etc/profile.d and /etc/.login.d respectively, allowing packages to easily add bits and pieces to the system login initialization by simply dropping files into those directories.

This issue covers adding those directories to illumos, and breaking out the existing init code into modular components in them. This will in some ways help out with things such as issue #2617, by allowing distributions to remove pieces of the global init they don't want without having to maintain a locally modified copy of the entire script.