Use #pragma once

Instead of

-#ifndef SHARE_VM_OOPS_KLASS_HPP
-#define SHARE_VM_OOPS_KLASS_HPP
+#pragma once
...
-#endif // SHARE_VM_OOPS_KLASS_HPP

Since the repository consolidation, the #define names reflect the old directory structure and are wrong. Rather than fix these and continue with this error-prone method, use #pragma once, which all modern compilers support.