fyi: COMDAT linkage -> less LLVM optimization

[Johan Engelen via digitalmars-d-ldc]

We emit most functions in COMDAT sections, but with LLVM 3.9 we 
loose out on some optimizations:
http://llvm.org/releases/3.9.0/docs/ReleaseNotes.html#changes-to-llvm-s-ipo-model

Don't know what the impact will be.
(I've always disliked putting everything in COMDAT sections, so 
it's extra ammunition against that)

-Johan