[foreign-jextract] Integrated: 8253390: jextract should quote string literals

[Athijegannathan Sundararajan]

String literals are escaped.

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

Commit messages:
 - 8253390: jextract should quote string literals

Changes: https://git.openjdk.java.net/panama-foreign/pull/351/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=351&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253390
  Stats: 56 lines in 3 files changed: 54 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/351.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/351/head:pull/351

PR: https://git.openjdk.java.net/panama-foreign/pull/351