[foreign-jextract] [Rev 03] RFR: 8246341: jextract should generate Cpointer utilities class

[Athijegannathan Sundararajan]

> Added Cpointer utilities class to deal with pointer values from C code.

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last
revision:

  * added asArray to C-X.java.template
  * make Cpointer API similar to other types like Cint, Cfloat etc.
  * Expanded Cpointer tesing a bit

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/191/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/191/files/7ea6bf38..85f73d0d

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/191/webrev.03
 - incr: https://webrevs.openjdk.java.net/panama-foreign/191/webrev.02-03

  Stats: 71 lines in 5 files changed: 65 ins; 4 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/191.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/191/head:pull/191

PR: https://git.openjdk.java.net/panama-foreign/pull/191