Now that llc can read .ll files directly, teach it to recognize .ll as

Now that llc can read .ll files directly, teach it to recognize .ll as
an extension, so that the default output filename for foo.ll is foo.s,
not foo.ll.s

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82071 91177308-0d34-0410-b5e6-96231b3b80d8