Merge remote-tracking branch 'apache/master' into error-handling

core/src/main/scala/org/apache/spark/Aggregator.scala

core/src/main/scala/org/apache/spark/SparkContext.scala

core/src/main/scala/org/apache/spark/SparkEnv.scala

core/src/main/scala/org/apache/spark/executor/Executor.scala

core/src/main/scala/org/apache/spark/rdd/CoGroupedRDD.scala

core/src/main/scala/org/apache/spark/rdd/HadoopRDD.scala

core/src/main/scala/org/apache/spark/rdd/NewHadoopRDD.scala

...rc/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala

core/src/main/scala/org/apache/spark/storage/BlockId.scala

...rc/main/scala/org/apache/spark/storage/BlockManager.scala

...in/scala/org/apache/spark/storage/BlockObjectWriter.scala

...ain/scala/org/apache/spark/storage/DiskBlockManager.scala

core/src/main/scala/org/apache/spark/ui/jobs/StagePage.scala

.../src/main/scala/org/apache/spark/ui/jobs/StageTable.scala

core/src/main/scala/org/apache/spark/util/Utils.scala

core/src/main/scala/org/apache/spark/util/Vector.scala

...cala/org/apache/spark/util/collection/AppendOnlyMap.scala

.../apache/spark/util/collection/ExternalAppendOnlyMap.scala

...che/spark/util/collection/SizeTrackingAppendOnlyMap.scala

...rg/apache/spark/util/SizeTrackingAppendOnlyMapSuite.scala