[JENKINS-20074] When displaying an uncaught exception, if we are unable to write the content, just do nothing.
Needs to build now with '-A'

This is presumably related to https://github.com/jenkinsci/jenkins/pull/956
but I don't fully understand what difference this makes.
[FIXED JENKINS-20191] Add Test button to check proxy connection
improved localization (de)

thanks to kutzi for spotting this.
Completing the migration to Java6
Better diagnosis for null parent.
Observed in 1.509.3:
java.lang.NullPointerException
	at hudson.model.AbstractItem.getRootDir(AbstractItem.java:162)
	at hudson.model.Items.getConfigFile(Items.java:236)
	at hudson.model.AbstractItem.getConfigFile(AbstractItem.java:461)
	at hudson.model.AbstractItem.save(AbstractItem.java:456)
	at hudson.model.Job.save(Job.java:152)
	at hudson.model.AbstractProject.save(AbstractProject.java:268)
	at hudson.diagnosis.OldDataMonitor.doDiscard(OldDataMonitor.java:275)
Merge branch 'master' of github.com:jenkinsci/jenkins
Missing @since.
Fork the compiler jvm.
Merge branch 'master' of github.com:jenkinsci/jenkins
Deprecating hudson field; use jenkins instead.
It is Thread.getThreadGroup that can return null, not ThreadGroup.getName.
https://jenkins.ci.cloudbees.com/job/core/job/jenkins_main_trunk/1436/testReport/hudson.model/UpdateCenter2Test/install/
java.lang.NullPointerException: null
	at hudson.Functions$ThreadSorterBase.<init>(Functions.java:1151)
	at hudson.Functions$ThreadSorterBase.<init>(Functions.java:1142)
	at hudson.Functions$ThreadGroupMap.<init>(Functions.java:1163)
	at hudson.Functions.sortThreadsAndGetGroupMap(Functions.java:1136)
	at org.jvnet.hudson.test.JenkinsRule$2.evaluate(JenkinsRule.java:482)
Synchronizing XPath-related assertions with implementations in HudsonTestCase, using HtmlUnit’s XPath engine rather than Hamcrest’s which does not seem to work in this context at least.
Deprecating SFTPClient.
fixed typo
Use Common HttpClient instead of URLConnection
Updated Japanese localization
[JENKINS-20280] Make it easy to change the implementation. Especially Map.Entry is not so convenient to handle.
[JENKINS-20280] Use topological sorting to decide the order to override variables.
NPE reported in 1.509.3 from OldDataMonitor as part of a general startup failure.
In this case display the reported exceptions differently and be done with it.
java.lang.NullPointerException
	at hudson.diagnosis.OldDataMonitor.report(OldDataMonitor.java:178)
	at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:312)
	at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:222)
	at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)