Detect uses of mismatching forms of 'new' and 'delete'

Detect uses of mismatching forms of 'new' and 'delete'

Emit warning when operand to `delete` is allocated with `new[]` or
operand to `delete[]` is allocated with `new`.

rev 2 update:
`getNewExprFromInitListOrExpr` should return `dyn_cast_or_null`
instead of `dyn_cast`, since `E` might be null.

Reviewers: rtrieu, jordan_rose, rsmith

Subscribers: majnemer, cfe-commits

Differential Revision: http://reviews.llvm.org/D4661

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237608 91177308-0d34-0410-b5e6-96231b3b80d8