Add support for new openSUSE Leap releases. Moreover, document
common environment variables and remove old note.
Change-Id: I8cf0b215cb4d9231e5658d49e3fd598dfbb5fd37
Updates the various operating system elements so that we
set the DISTRO_NAME variable for each distro.
This env var is used by bin/pkg-map to set the default
distribution name for package name mappings.
Change-Id: Ib4b05eb7191dd50d25799a0bac51fd15c01b74cb