Reviewed-by: dholmes, erikj

Summary: Improve the nmethod unloading times by optimizing the search for an itable stub in VtableStubs array
Reviewed-by: kvn, coleenp, tschatzl

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

Summary: remove speculative traps that point to methods that are redefined
Reviewed-by: kvn, twisti

Reviewed-by: dholmes, phh

Reviewed-by: kvn

Reviewed-by: coleenp, eosterlund, mchung, ahgross, rhalade