* Reorder software requirements list to show relative importance
* Use superscripts for footnotes in software list rather than "Note 1"
* Use new doc_notes class to separate footnotes from main doc text
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20098 91177308-0d34-0410-b5e6-96231b3b80d8