Diagnose attributes 'optnone' and 'minsize' on the same declaration.

Eventually we'll diagnose them on different declarations, but let's
get this part out of the way first.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@223985 91177308-0d34-0410-b5e6-96231b3b80d8