Don't attempt to validate the output of %p.

In one of the ostream tests we attempt to validate whether the output of
%p is correct. This is actually outside the scope of libc++, for the
%reason that the format of %p is implementation defined. Change the test
%to validate that the output of %p is non-empty and is different when
%given two unequal addresses.

Differential Revision:	http://reviews.llvm.org/D8354
Reviewed by:	marshall

llvm-svn: 232390