Added HPPC_ITERATOR_POOLSIZE property
in order to control the number of pre-allocated iterators per pool
through a property. This also allowed to fix the iterator pools unit tests to fail
on non-multicores machines.
Merge branch '0.6.x-RT' of https://github.com/vsonnier/hppc into 0.6.x-RT

Conflicts:
	binaries/hppc-RT-0.6.0-SNAPSHOT-jdk15.jar
	hppc-core/src/main/java/com/carrotsearch/hppc/IteratorPool.java