Something¹ seems to interrupt the HTTP duplex service thread,
and Jetty apparently deals poorly with interruptions.
So introduce an extra sleep to soak up the interrupt.

¹Who? http://stackoverflow.com/questions/2126997/who-is-calling-the-java-thread-interrupt-method-if-im-not#comment40865453_2127397

Jetty 9.4.3.v20170317 refuses to set an empty HTTP header, leading to cryptic client errors since Hudson-Duplex is missing.

[JENKINS-27624][JENKINS-42709] Bump Jenkins baseline to Java 8 minimum

[JENKINS-43320] Improve JNLP configuration Spanish translations

Making interrupt of `build -s` work in `-http` mode.
Does not solve `ReadPendingException`s.

Using kill -QUIT to try to diagnose client hangs observed on ci.jenkins.io but not locally reproducible.

java.nio.file.FileSystemException: …\.ssh\known_hosts: Incorrect function.
        at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:86)
        at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:90)
        at sun.nio.fs.WindowsAclFileAttributeView.getFileSecurity(WindowsAclFileAttributeView.java:88)
        at sun.nio.fs.WindowsAclFileAttributeView.getOwner(WindowsAclFileAttributeView.java:121)
        at sun.nio.fs.FileOwnerAttributeViewImpl.getOwner(FileOwnerAttributeViewImpl.java:91)
        at java.nio.file.Files.getOwner(Files.java:2079)
        at org.apache.sshd.common.util.io.IoUtils.getFileOwner(IoUtils.java:272)
        at org.apache.sshd.common.util.io.ModifiableFileWatcher.validateStrictConfigFilePermissions(ModifiableFileWatcher.java:240)
        at org.apache.sshd.client.keyverifier.DefaultKnownHostsServerKeyVerifier.reloadKnownHosts(DefaultKnownHostsServerKeyVerifier.java:79)
        at org.apache.sshd.client.keyverifier.KnownHostsServerKeyVerifier.verifyServerKey(KnownHostsServerKeyVerifier.java:161)
        at …
Interactive testing of known_hosts on XP works as expected.

[JENKINS-36720] - Cleanup of SOME medium FindBugs issues

Obsolete with Java 8. Permanent generation was removed.

[JENKINS-34670] Add support for a new full screen layout

[JENKINS-42744] - Update WinSW to 2.0.3 and Windows Agent installer t0 1.8

This PR updates WinSW to 2.0.3 in order to fix [JENKINS-42744](https://issues.jenkins-ci.org/browse/JENKINS-42744), which is reported as a critical regression in Jenkins 2.50.

Changelog: https://github.com/kohsuke/winsw/blob/master/CHANGELOG.md#203

Full diff: https://github.com/kohsuke/winsw/compare/winsw-2.0.2...winsw-2.0.3

And suppress associated workaround

[JENKINS-42934] Avoid using new FileInputStream / new FileOutputStream

Remove invalid CSS rule