* src/vm/global.h: Made 'lockword' member of java_object_t a plain

* src/vm/global.h: Made 'lockword' member of java_object_t a plain
integer type because offsetof works only on POD structs (and gcc
complains about that).
* src/threads/lockword.hpp: Lockword references its data member now
instead of containing it.
* src/threads/lock.cpp: Adapted to new Lockword signature.
* src/vm/array.hpp: Likewise.
* src/vm/class.cpp: Likewise.
* src/vm/jit/builtin.cpp: Likewise.
* src/vm/string.cpp: Likewise.