RFR: 8275097: Wrong span of the 'default' tag

[Jan Lahoda]

The span of the 'default' case label AST node is wrong when `default:` is encountered. This patch fixes the positions to be reasonable (i.e. the span of the AST node should be the characters 'default').

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Commit messages:
 - 8275097: Wrong span of the 'default' tag

Changes: https://git.openjdk.java.net/jdk/pull/5905/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5905&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275097
  Stats: 96 lines in 3 files changed: 89 ins; 3 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5905.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5905/head:pull/5905

PR: https://git.openjdk.java.net/jdk/pull/5905