[PATCH] Fix for libc++ bug #20096 http://llvm.org/bugs/show_bug.cgi?id=20096

[Eric Fiselier]

================
Comment at: test/utilities/meta/meta.unary/meta.unary.prop/is_destructible.pass.cpp:55-58
@@ -54,1 +54,6 @@
 
+class AbstractDestructor
+{
+    virtual ~AbstractDestructor() = 0;
+};
+
----------------
Since the destructor is private, this tests access control SFINAE and not the abstract destructor. After making the abstract destructor public, this test fails for both C++11 and C++03.

http://reviews.llvm.org/D4306