Bug #:

Submitted by:
Reviewed by:
Fix two bugs...

- Sema::CheckConditionalOperands(). Needed to move the check for
null pointer constants up to the clause dealing with two pointers types.
The previous code would never get executed.
- Expr::isNullPointerConstant(). This predicate was much too naive...it
should have had a FIXME (my bad). It now deals with "void *" cast expressions.
It still has one major bug...it needs to evaluate the expression to correctly
determine if it is a null pointer constant (e.g. 7-7 should pass).

llvm-svn: 39464