[foreign-jextract] RFR: * adding Windows scripts (Thanks @jvernee)

[Athijegannathan Sundararajan]

On Mon, 27 Jul 2020 12:57:25 GMT, Athijegannathan Sundararajan <sundar at openjdk.org> wrote:

> * adding OpenGL sample (Thanks @mcimadamore)
> 
> added Windows scripts and OpenGL sample

This will be simplified and a fresh PR will be raised later

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PR: https://git.openjdk.java.net/panama-foreign/pull/265