RFR (S): 8024067: Missing replace_in_map() calls following null checks

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8024067/webrev.00/

For the replace_in_map() in GraphKit::maybe_cast_profiled_receiver() to propagate the type change, we must first call replace_in_map on the result of the null checks when it's ok to do so. In a subsequent change, I intend for safe_for_replace to be an argument to GraphKit::gen_instanceof() and allow the replace_in_map calls to be done for the Class.isInstance intrinsic but that requires some form of profiling there first.

Roland.