[LOG4J2-685] Make org.apache.logging.log4j.core.layout.AbstractLayout immutable.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1605486 13f79535-47bb-0310-9956-ffa450edef68
[LOG4J2-686] Core's OptionConverter support for \b is broken (affects PatternLayout).

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1605494 13f79535-47bb-0310-9956-ffa450edef68
[LOG4J2-687] Rename org.apache.logging.log4j.core.util.Closer.closeSilent() to closeSilently().

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1605496 13f79535-47bb-0310-9956-ffa450edef68
Remove duplicate code.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1605502 13f79535-47bb-0310-9956-ffa450edef68
Rename test method.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1605504 13f79535-47bb-0310-9956-ffa450edef68