Merge branch 'stable-5.6'

Merge branch 'stable-5.6'

* stable-5.6:
  Fix API problem filters
  Fix unclosed resource warning in SmartOutputStream
  JschConfigSessionFactory: fix boxing warning
  SshSupport#runSshCommand: don't throw exception in finally block
  Don't override already managed maven-compiler-plugin version
  Remove unused import from CreateFileSnapshotBenchmark
  Remove duplicate ignore_optional_problems entry in .classpath
  Update maven-site-plugin used by benchmark module to 3.8.2
  Add dependency to enable site generation for benchmark module
  Ignore warnings for generated source code in
org.eclipse.jgit.benchmark
  Fix MBean registration
  Enhance WindowCache statistics

Change-Id: I4a77c602bfffed60535d0b8fc251a552b128068d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>