mozilla/rust — pull request #7947 by roysc (2013-07-21 20:52:03+00:00)
Title: Make `rust-mode` derive from `prog-mode` if available

This let rust-mode be classified as a programming mode, which is only relevant to Emacs 24.x. This way, for example, `prog-mode-hook`s can be run when entering `rust-mode`.