Added the ability to dereference an Objective-C object

pointer to make the result of an expression.  LLDB now
dumps the ivars of the Objective-C object and all of
its parents.  This just required fixing a bug where we
didn't distinguish between Objective-C object pointers
and regular C-style pointers.

Also added a testcase to verify that this continues to
work.

llvm-svn: 146164