clang-format: Make SFS_Inline imply SFS_Empty.

In the long run, these two might be independent or we might to only
allow specific combinations. Until we have a corresponding request,
however, it is hard to do the right thing and choose the right
configuration options. Thus, just don't touch the options yet and
just modify the behavior slightly.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@239531 91177308-0d34-0410-b5e6-96231b3b80d8