RFR: 8281275: Upgrading from 8 to 11 no longer accepts '/' as filepath separator in gc paths

[David Holmes]

Please review this trivial fix for UL parsing logic on Windows. We already special-cased paths like c:\logfile but didn't allow for c:/logfile. As noted in the bug report this is a regression from using -Xloggc where the c:/ path was allowed (and it even worked when Xloggc was converted internally to use UL - because it skipped the parsing logic and just directly set the file output!).

Testing:
  - new gtest added by expanding existing parsing gtest
  - tiers 1-3 Windows

Verified that new gtest fails without the fix.

Thanks,
David

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Commit messages:
 - Fix style issue
 - 8281275: Upgrading from 8 to 11 no longer accepts '/' as filepath separator in gc paths

Changes: https://git.openjdk.java.net/jdk/pull/7415/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7415&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281275
  Stats: 28 lines in 2 files changed: 23 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7415.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7415/head:pull/7415

PR: https://git.openjdk.java.net/jdk/pull/7415