PIG-3148: OutOfMemory exception while spilling stale DefaultDataBag. Extra option to gc() before spilling large bag. (knoguchi via rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/trunk@1452226 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'trunk' of https://github.com/apache/pig into trunk