RFR: CODETOOLS-7902936 Stray VM warnings in forked PrintPropertiesMain lead to hard to debug XML parse exception

[Jason Zaugg]

- Recover from stray output before the XML prelude
  - Report the output in the exception otherwise
  - Silence VM warnings in PrintPropertiesMain when JEP-158 (-Xlog:) is available (JRE 9+)

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

Commit messages:
 - Disable VM warnings polluting XML on stdout
 - Recover or report stray VM output from PrintPropertiesMain

Changes: https://git.openjdk.java.net/jmh/pull/41/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmh&pr=41&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902936
  Stats: 21 lines in 2 files changed: 19 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jmh/pull/41.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/41/head:pull/41

PR: https://git.openjdk.java.net/jmh/pull/41