[foreign-abi] RFR: 8253373: Add package-level javadoc for foreign linker support [v4]

[Maurizio Cimadamore]

> This patch modifies the toplevel javadoc of jdk.incubator.foreign to add details about the ABI support.
> 
> I've decided to split the javadoc into two main sections - one about memory access, and one about foreign function
> access; they have subsections for more detailed info.
> There's also a trailing toplevel section on "restricted method". I'm still wordsmithing the definition of "what's it
> like to be a restricted method" together with Alex, but this is a first attempt. It is likely that, once we have this
> done, we can have the various restrcited definitions inside the API refer bakc to this section.
> Link to javadoc:
> http://cr.openjdk.java.net/~mcimadamore/panama/foreign-linker-javadoc/javadoc/jdk/incubator/foreign/package-summary.html

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Tweak call to LibraryLookup in javadoc

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

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/346/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/346/files/1f3b9fca..665a0f02

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=346&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=346&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/346.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/346/head:pull/346

PR: https://git.openjdk.java.net/panama-foreign/pull/346