[foreign-jextract] RFR: 8252016: jextract should handle va_list [v4]

[Athijegannathan Sundararajan]

> adding va_list support for jextract

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

  Inserted whitespace after variadic. Removed unused import in RuntimeHelper.

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

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/285/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/285/files/6520f0aa..b42e237b

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/285/webrev.03
 - incr: https://webrevs.openjdk.java.net/panama-foreign/285/webrev.02-03

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/285.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/285/head:pull/285

PR: https://git.openjdk.java.net/panama-foreign/pull/285