[FIXED JENKINS-19976] Enable plugins to load classes from optionally depending plugins even without restarting after depended ones installed.
[JENKINS-19976] Tests for the behavior of loading a depended plugin dynamically.
[JENKINS-19976] Added tests how dynamic load works for @Extension.
[JENKINS-19976] Added plugins to test dynamic loading.
Merge branch 'feature/JENKINS-19976_TestForInstallDepended' into feature/JENKINS-19976_LoadClassFromNewInstalledPlugin
[JENKINS-19976] Fixed confusing comments.
[FIXED JENKINS-21855] Add preview for parameter descriptions
Javadoc for Queue.Task claimed they were compared using .equals(), but in critical cases this was not actually true.
Does not matter for the common case of Job, but when implementing custom tasks this could cause duplicate queue items (and executables).
Slave started from JNLP can now install itself as systemd service.
Upgrade to commons-io 2.4

In order to maintain backwards compatibility we need to keep IOUtils the
same as in commons-io 1.4. This code is backwards compatible, however
most of the methods have been deprecated and should instead use the
org.apache.commons.io.IOUtils version instead.
Merge pull request #1135 from christ66/commons-io-up

Upgrade to commons-io 2.4
typo in changelog
[FIXED JENKINS-12124] Occasionally errors loading plugin classes since it is expected that findClass (and findLoadedClass) are called under synchronization.
The problem was masked by a blind assumption that an InvocationTargetException was in fact wrapping a ClassNotFoundException.
Many thanks to @gotwarlost for demonstrating how to reproduce the problem and diagnosing the cause.
Disabling systemd-slave-installer until it can be fixed to be quiet on Ubuntu.
Fixed systemd error on Ubuntu that Jesse found.
[FIXED JENKINS-20965] Run.writeWholeLogTo causes high CPU usage.
Wait one second before writing to log files. Switched to while loop to
prevent extra one second delay.
Deprecate the static final variables used in IOUtils.
Merge pull request #1138 from christ66/commons-io-up

Deprecate the static final variables used in IOUtils.
Merge branch 'JENKINS-20965' of github.com:christ66/jenkins
[JENKINS-20965] Noting merge of #1137.