maven plugin is moved off to a separate repository.

See https://github.com/jenkinsci/maven-plugin
[JENKINS-19473] Removing workaround since root bug should be fixed in jzlib 1.1.3.
Moving hudson.maven tests to maven-plugin.
Migrated some usages of GNUCLibrary to the jnr PosixAPI, fixed 'mvn -Plight-test install' on ubuntu with OpenJDK.
Moving one test case to maven-plugin.
Remove unused import.
Copy basic Surefire configuration, esp. forkCount=2, to the plugin POM.
Shaves >11min off the test time for maven-plugin on my machine!
Merge pull request #967 from akiellor/fix-local-build-issues

Fix `mvn -Plight-test install` on Ubuntu 13.04 with OpenJDK
Merge branch 'master' of github.com:jenkinsci/jenkins
Removing test dep on ui-samples.
Superfluous in that if you *want* to look at UI samples, you can just install that plugin.
And observed to cause a cyclic plugin dependency error when splitting matrix-auth from core.
(Unclear why ui-samples had a dependency on matrix-auth; perhaps related to dependency from test module.)
Split off matrix-auth plugin.
matrix-auth 1.0.2 (couple of fixups)
Split out ui-samples-plugin into its own repo.
ClassicPluginStrategy.DETACHED_LIST could confuse ClassicPluginStrategyTest by injecting dependencies on split plugins that have an index.jelly.