8156137: SIGSEGV in ReceiverTypeData::clean_weak_klass_links
8057570: RedefineClasses() tests fail assert(((Metadata*)obj)->is_valid()) failed: obj is valid
Reviewed-by: coleenp

Reviewed-by: mgerdin, coleenp, bdelsart

Reviewed-by: tschatzl, ehelin, brutisso, coleenp, roland, iveresov
Contributed-by: stefan.karlsson@oracle.com, mikael.gerdin@oracle.com

Reviewed-by: coleenp, sspitsyn, mgronlun

8026948: JvmtiEnv::SetBreakpoint and JvmtiEnv::ClearBreakpoint might not work with anonymous classes
Summary: Walk methods in breakpoints for marking on stack so they aren't deallocated by redefine classes.  Use class_holder rather than class_loader to keep GC from reclaiming class owning the method.
Reviewed-by: sspitsyn, ehelin, sla

Summary: Added on_stack bit to flags.  Also MetadataMarkOnStack is used for more than JVMTI so had to be moved.
Reviewed-by: dholmes, stefank