[foreign-jextract] RFR: adding sqlite3 sample

[Athijegannathan Sundararajan]

This demo uses the recent Cpointer, Cscope features.

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Commit messages:
 - adding sqlite3 sample

Changes: https://git.openjdk.java.net/panama-foreign/pull/193/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/193/webrev.00
  Stats: 233 lines in 2 files changed: 233 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/193.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/193/head:pull/193

PR: https://git.openjdk.java.net/panama-foreign/pull/193