[foreign-abi] RFR: 8253430: Improve the LibraryLookup API [v2]

[Maurizio Cimadamore]

> This patch implements a couple of suggestion which were made a couple of weeks ago by @BlueGoliath - here:
> 
> https://mail.openjdk.java.net/pipermail/panama-dev/2020-July/010140.html
> 
> Two ideas here:
> * Change the signature of `LibraryLookup::ofPath` to actually take a `Path` (rathar than a `String`)
> * Tweak `LibraryLookup::lookup` to return `Optional` (rather than throw)
> 
> Both suggestions seem to change the API for the better. The second one is probably more controversial: on the one hand
> it removes the need for having exception handling logic and makes it for more composable logic. On the other hand
> clients have to manually call `get` on the lookup result. But overall seems a win.

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

  Require absolute path on LibraryLookup::ofPath

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

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/348/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/348/files/072e97ed..265a76ec

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=348&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=348&range=00-01

  Stats: 15 lines in 2 files changed: 10 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/348.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/348/head:pull/348

PR: https://git.openjdk.java.net/panama-foreign/pull/348