Move checks for creation of objects of abstract class type from the various

constructs that can do so into the initialization code. This fixes a number
of different cases in which we used to fail to check for abstract types.

Thanks to Tim Shen for inspiring the weird code that uncovered this!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289753 91177308-0d34-0410-b5e6-96231b3b80d8