Define the KM_NORMALPRI flag for kmem_alloc(), as it is used in some
upstream DTrace code. It indicates that the kernel memory allocator need not
attempt to satisfy non-blocking allocations in low-memory conditions. This
has no direct equivalent in the malloc(9) flags, so it is just defined to 0
for now.
1452 DTrace buffer autoscaling should be less violent

illumos/illumos-gate@6fb4854bed54ce82bd8610896b64ddebcd4af706

This fixes the tst.resize1.d and tst.resize2.d DTrace tests, which have
been failing since r261122 since they were causing dtrace(1) to attempt to
allocate and use large amounts of memory, and get killed by the OOM killer
as a result.

MFC after:	1 month