Link together the call operator produced from transforming a lambda

expression with the original call operator, so that we don't try to
separately instantiate the call operator. Test and tweak a few more
bits for template instantiation of lambda expressions.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150440 91177308-0d34-0410-b5e6-96231b3b80d8