RFR: 8276549: Improve documentation about ContainerPtr encoding [v2]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this trivial? change to add some more documentation to `G1CardSet::ContainerPtr`?
> 
> Testing: local compilation
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  Add "Free" to Howl container doc

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8811/files
  - new: https://git.openjdk.java.net/jdk/pull/8811/files/105f7e97..3b1b68ad

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8811&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8811&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8811.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8811/head:pull/8811

PR: https://git.openjdk.java.net/jdk/pull/8811