Fix a leak in HNI ActRec functions

Summary: They don't free their extraArgs. Since the main reason
for using an ActRec function is to allow extra arguments, this
seems like it might be quite common.

Reviewed By: @edwinsmith, @jdelong

Differential Revision: D1580527
ArrayUtil::RegularSortUnique(): pre-allocate array based on unique count

Reviewed By: @elgenie

Differential Revision: D1580109