[jdk16] RFR: JDK-8258916: javac/doclint reports broken HTML on multiline mailto links

[Jonathan Gibbons]

Please review a trivial fix to correctly handle '@' inside the value of an HTML attribute. 
The fix is simply to cancel the `newline` flag that is set when a newline has been read.

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Commit messages:
 - JDK-8258916: javac reports broken HTML on multiline mailto links

Changes: https://git.openjdk.java.net/jdk16/pull/68/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16&pr=68&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258916
  Stats: 8 lines in 2 files changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/68.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/68/head:pull/68

PR: https://git.openjdk.java.net/jdk16/pull/68