RFR: 8265914: Duplicated NotANode and not_a_node

[Yi Yang]

NotANode(node.hpp) and not_a_node(compile.cpp) are completely repeated guys.

-------------

Commit messages:
 - not_a_node

Changes: https://git.openjdk.java.net/jdk/pull/3715/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3715&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265914
  Stats: 36 lines in 5 files changed: 0 ins; 14 del; 22 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3715.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3715/head:pull/3715

PR: https://git.openjdk.java.net/jdk/pull/3715