HADOOP-11250. fix endmacro of set_find_shared_library_without_version in CMakeLists (Yi Liu via Colin P. McCabe)
(cherry picked from commit e488f0d93bf22d25aaaac7a6a88fc300f9aa6d5a)
(cherry picked from commit e107ea5177776bbe14178859a53740f72a46b64b)
HDFS-7230. Add rolling downgrade documentation. Contributed by Tsz Wo Nicholas Sze.

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
HADOOP-11221. IdentityHashStore assumes System.identityHashCode() is non-negative. Contributed by Jinghui Wang
HADOOP-11247. Fix a couple javac warnings in NFS. Contributed by Brandon Li.

(cherry picked from commit c7d1db7495e772ff81077b3865337838eded025a)

Conflicts:
	hadoop-common-project/hadoop-common/CHANGES.txt