docs: Inline documentation structure into homepage.

This brings back {Ctrl,Cmd}-f'ability, and makes some really bad
organizational choices easier to see (and therefore fix).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172949 91177308-0d34-0410-b5e6-96231b3b80d8
docs: Use proper markup.

These are really definition lists.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172950 91177308-0d34-0410-b5e6-96231b3b80d8