Sema: Instantiate local class and their members appropriately

We would fail to instantiate them when the surrounding function was
instantiated. Instantiate the class and add it's members to the list of
pending instantiations, they should be resolved when we are finished
with the function's body.

This fixes PR9685.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195827 91177308-0d34-0410-b5e6-96231b3b80d8