Support overloading of the subscript operator[], including support for
built-in operator candidates. Test overloading of '&' and ','.

In C++, a comma expression is an lvalue if its right-hand
subexpression is an lvalue. Update Expr::isLvalue accordingly.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59643 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed