User:Veremit/wiki tidyup

Debugging

 * https://wiki.gentoo.org/wiki/Debugging
 * https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces

Custom overlays

 * https://wiki.gentoo.org/wiki/Custom_repository
 * https://wiki.gentoo.org/wiki/Handbook:AMD64/Portage/CustomTree