Rewrite Expr::isNullPointerConstant() to deal with multiple levels of explicit casts.

Now, isNullPointerConstant() will return true for the following: "(void*)(double*)0"



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@45951 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed