RFR: 8265106: IGV: Enforce en-US locale while parsing ideal graph

[Yi Yang]

IGV is designed to support parsing incomplete XML. However, it does not work for non-English users. See XXPR for the detailed reasons. This patch would address it.

(P.S. Locale.ENGLISH also does not work, see  Philip Helger' [comment](https://stackoverflow.com/questions/18531633/locale-specific-messages-in-xerces-2-11-0-java) on the first answer.)

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Commit messages:
 - parse incomplete xml

Changes: https://git.openjdk.java.net/jdk/pull/3563/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3563&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265106
  Stats: 9 lines in 2 files changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3563.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3563/head:pull/3563

PR: https://git.openjdk.java.net/jdk/pull/3563