RFR: 7903758: jextract should avoid temporary file creation [v4]

[Athijegannathan Sundararajan]

> jextract creates a temporary file to support multiple headers and special header syntax <foo.h>. This patch avoids that temporary file creation by using clang's in-memory parsing API clang_createTranslationUnitFromSourceFile

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

  Using clang_parseTranslationUnit2 instead of clang_createTranslationUnitFromSourceFile.

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Changes:
  - all: https://git.openjdk.org/jextract/pull/251/files
  - new: https://git.openjdk.org/jextract/pull/251/files/8ca6c525..267c889d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=251&range=03
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=251&range=02-03

  Stats: 116 lines in 3 files changed: 17 ins; 85 del; 14 mod
  Patch: https://git.openjdk.org/jextract/pull/251.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/251/head:pull/251

PR: https://git.openjdk.org/jextract/pull/251