svn merge -c 1605239 from trunk for HADOOP-10674. Improve PureJavaCrc32 performance and use java.util.zip.CRC32 for Java 7 and above.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1605240 13f79535-47bb-0310-9956-ffa450edef68