RFR: 8258048: Placeholder hash code is the same as Dictionary hash code [v2]

[Coleen Phillimore]

> This change is a set of cleanups to the placeholders hashtable.  It moves the index calculation inside the hashtable.  It avoids using the placeholder hashcode because it's the same hashcode as the dictionary hashcode.  There are some asserts for this.
> 
> One of the find_class() functions is redundant to dictionary->find_class() so is removed.
> 
> Tested with tier1-6.

Coleen Phillimore has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into class-loading
 - 8258048: Placeholder hash code is the same as Dictionary hash code

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1789/files
  - new: https://git.openjdk.java.net/jdk/pull/1789/files/0071785f..ddf96fa2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1789&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1789&range=00-01

  Stats: 1778 lines in 52 files changed: 906 ins; 756 del; 116 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1789.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1789/head:pull/1789

PR: https://git.openjdk.java.net/jdk/pull/1789