From: Brian Behlendorf <behlendorf1@llnl.gov>
Subject: [PATCH] fix stack dmu_objset_snapshot

Reduce stack usage by 276 bytes by moving the snaparg struct from the
stack to the heap.  We have limited stack space we must not waste.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>