Improve emacs coding style

Remove setting of default style, this way is not recommended and
means that all the settings have to be duplicated to demonstrate the
c-add-style method which is a much better way of doing it.

Remove the modified date as it is better stored in SVN.

Tweak a few style parameters to make them conform to the actual LLVM
style.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223765 91177308-0d34-0410-b5e6-96231b3b80d8