C++1y: Allow aggregates to have default initializers.

Add a CXXDefaultInitExpr, analogous to CXXDefaultArgExpr, and use it both in
CXXCtorInitializers and in InitListExprs to represent a default initializer.

There's an additional complication here: because the default initializer can
refer to the initialized object via its 'this' pointer, we need to make sure
that 'this' points to the right thing within the evaluation.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179958 91177308-0d34-0410-b5e6-96231b3b80d8
Add another test I forgot to svn add.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179959 91177308-0d34-0410-b5e6-96231b3b80d8
Disable VLA diagnostic in C++1y mode, and add some tests.

Still to do here:
  - we have a collection of syntactic accepts-invalids to diagnose
  - support non-PODs in VLAs, including dynamic initialization /
    destruction
  - runtime checks (and throw std::bad_array_length) for bad bound
  - support VLA capture by reference in lambdas
  - properly support VLAs in range-based for (don't recompute bound)


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179962 91177308-0d34-0410-b5e6-96231b3b80d8
The 'constexpr implies const' rule for non-static member functions is gone in
C++1y, so stop adding the 'const' there. Provide a compatibility warning for
code relying on this in C++11, with a fix-it hint. Update our lazily-written
tests to add the const, except for those ones which were testing our
implementation of this rule.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179969 91177308-0d34-0410-b5e6-96231b3b80d8