[PATCH] Fix failure in noexcept when the argument is a call to constexpr function

[Richard Smith]

  I'm afraid the direction of this change isn't correct. If **any** call within the `noexcept` expression's operand is a constant expression (not just a top-level call expression), the exception specification of that call is ignored. It's also not worth addressing this right now -- the entire implementation of `canThrow` is going to be ripped out and reimplemented for core issue 1351, for which I have a near-complete patch.

http://llvm-reviews.chandlerc.com/D2123