PR156: Preparation

PR156: Preparation
* src/vm/javaobjects.cpp: Added a facility for registering dynamic field
offsets.
* src/vm/javaobjects.hpp (jobjects_register_dyn_offsets,
jobjects_run_dynoffsets_hook): Added.
* src/vm/hook.cpp: Added because of non-inline function.
* src/vm/hook.hpp (class_linked): Changed signature because of exception
handling.
(class_linked_dynoffsets): Added & call it.
* src/vm/linker.cpp: Adapted to new signatures.
* src/vm/linker.hpp: Cleanup only.
* src/vm/Makefile.am: Added hook.cpp.
* src/vm/vm.cpp: Call new dynamic offset hook.
* src/toolbox/hashtable.hpp: Cleanup only.