Various interrelated cleanups for lambdas:
  - Complete the lambda class when we finish the lambda expression
    (previously, it was left in the "being completed" state)
  - Actually return the LambdaExpr object and bind to the resulting
  temporary when needed.
  - Detect when cleanups are needed while capturing a variable into a
  lambda (e.g., due to default arguments in the copy constructor), and
  make sure those cleanups apply for the whole of the lambda
  expression.
    


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150123 91177308-0d34-0410-b5e6-96231b3b80d8
12 files changed