Fix RC 6 change log

Merge pull request oracle#231 in G/truffleruby from pitr-ch/patching …

…to master

* commit '74ba6cdb7e12d4a196584cc8250fe10f1f154efc':
  Simpler and more robust patching

Merge pull request oracle#162 in G/truffleruby from merge-release-rc2…

…-branch to master

* commit 'a628175aa00a045dc23dffb5b3fadf4b5bb72b6f': (29 commits)
  New CE/EE version string
  Run PE tests in Docker for --jvm
  Accommodate ce/ee prefix, and build suffix, in tarballs
  gu install --file now
  Ubuntu needs the post-install hook to be run
  gu install -c org.graalvm.ruby is now gu install org.graalvm.ruby
  Remove old Docker infrastructure
  Missing keep file
  Fixes
  Use ENV rather than a wrapper script
  Use fetch rather than normal hash lookup in the Docker tool
  Hardcode the working directory code in Docker
  Update version regexp
  Tidy up Docker command parsing
  Use full ruby-installable.jar name in documentation
  Re-arrange --rebuild-images logic
  Break up a long line
  Don't write Dockerfiles to the root directory
  --rebuild-images needs gcc
  jt docker tool
  ...

Merge pull request oracle#162 in G/truffleruby from merge-release-rc2…

…-branch to master

* commit 'a628175aa00a045dc23dffb5b3fadf4b5bb72b6f': (29 commits)
  New CE/EE version string
  Run PE tests in Docker for --jvm
  Accommodate ce/ee prefix, and build suffix, in tarballs
  gu install --file now
  Ubuntu needs the post-install hook to be run
  gu install -c org.graalvm.ruby is now gu install org.graalvm.ruby
  Remove old Docker infrastructure
  Missing keep file
  Fixes
  Use ENV rather than a wrapper script
  Use fetch rather than normal hash lookup in the Docker tool
  Hardcode the working directory code in Docker
  Update version regexp
  Tidy up Docker command parsing
  Use full ruby-installable.jar name in documentation
  Re-arrange --rebuild-images logic
  Break up a long line
  Don't write Dockerfiles to the root directory
  --rebuild-images needs gcc
  jt docker tool
  ...

New CE/EE version string

(cherry picked from commit af808ba)

Update imports.

Add slow tags for the pre-init spec when running on native

Merge pull request oracle#1149 from oracle/changelog

Tidy up the change log

update doc

Also build Sulong for integration tests