8048128: Fix for Solaris Studio C++ 5.13, CHECK_UNHANDLED_OOPS breaks PPC build.

Summary: Changes to successfully compile class oop within oops/oopsHierarchy.hpp for PPC build (with gcc 4.1.2).
Reviewed-by: dholmes, hseigel

src/share/vm/oops/oopsHierarchy.hpp

@@ -124,7 +124,7 @@ public:
   operator oopDesc* () const volatile { return obj(); }
   operator intptr_t* () const         { return (intptr_t*)obj(); }
   operator PromotedObject* () const   { return (PromotedObject*)obj(); }
-  operator markOop () const           { return markOop(obj()); }
+  operator markOop () const volatile  { return markOop(obj()); }
   operator address   () const         { return (address)obj(); }
 
   // from javaCalls.cpp