Implement DR1454. This allows all intermediate results in constant expressions
to be core constant expressions (including pointers and references to
temporaries), and makes constexpr calculations Turing-complete. A Turing machine
simulator is included as a testcase.

This opens up the possibilty of removing CCValue entirely, and removing some
copies from the constant evaluator in the process, but that cleanup is not part
of this change.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150557 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed