RFS(M): 8005031: Some cleanup in c2 to prepare for incremental inlining support

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8005031/webrev.00/

A collection of small changes that were found to be required for the upcoming incremental inlining support and that we intend to push first so that they be tested in isolation.

With incremental inlining, inlining doesn't happen in parse order anymore so the output of PrintInlining can get confusing. There's some support in this change to keep the PrintInlining output in order.

Regarding add_node.cpp, I noticed some nodes wouldn't be found as dead by the igvn. I assume it is a bug.

Roland.