Fix handling of PutArgStk

Fix handling of PutArgStk

GT_PUTARG_STK doesn't produce a value, so it should have the GTK_NOVALUE flag set.
Although the dstCount was being set to zero by the parent call, localDefUse was also being set, causing a register to be allocated. Fixing this produces a number of improvements due to reuse of constant registers that were otherwise unnecessarily "overwritten" by the localDefUse.
Also on x86, GT_LONG shouldn't be used to pass a long, since GT_LONG should always be a value-producing node. Instead, use the existing GT_FIELD_LIST approach.