Changes

In conjunction with the Linux community, we will define and maintain a reasonably modern and stable set of runtime requirements, and focus on supporting Mozilla apps to run against those requirements. These requirements may change over time, based on how the platform evolves. Distros providing longer-term support (i.e. enterprise distributions with long lifecycle requirements and older libraries) would then will be responsible for maintaining support for older runtimes via build-time switches. This is in line with how many other apps are supported by the distros.