RFR: 7903133: add lp_solve sample

[Athijegannathan Sundararajan]

Adding lp_solve jextract sample. This is more or less straight port of a C example.

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Commit messages:
 - removed trailing whitespaces in LpSolveDemo.java
 - 7903133: add lp_solve sample

Changes: https://git.openjdk.java.net/jextract/pull/7/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jextract&pr=7&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903133
  Stats: 166 lines in 7 files changed: 166 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jextract/pull/7.diff
  Fetch: git fetch https://git.openjdk.java.net/jextract pull/7/head:pull/7

PR: https://git.openjdk.java.net/jextract/pull/7