Build, path and permforance fixes for Linux compatibility

This patch fixes build issues on Linux (Ubuntu). This patch also detects which OS (FreeBSD or Linux) Lumina is building on and pulls in the proper OS-specific files during the build. Added OS-specific path names for non-Lumina components, such as icons, to make sure icons appear on desktop. Fixed bug causing 100% CPU usage and inability to logout. (All of these are minor tweaks which should enable Lumina to build on Linux without breaking compatibility with PC-BSD/FreeBSD).