* Started PKE sim unit testing. A number of minor errors were corrected.

* Started PKE sim unit testing.  A number of minor errors were corrected.
  A few PKE instructions even run correctly!  Next missing function of
  interest: FIFO pruning.

	* sky-pke.c (pke_issue): Take extra SIM_DESC argument.
	(pke_attach): Attach correct PKE0/PKE1 device.  Open trace file if
 	VIF{0,1}_TRACE_FILE env. var. is defined.
	(pke_io_write_buffer): Classify words in FIFO quadword.  Use
 	kludgey sim_core routines to access DMA registers.
	(pke_pc_advance): Add PKEcode classification.  Correct DMA tag
 	skipping.  Emit trace records.
	(pke_pc_fifo): Add PKEcode operand classification.
	(pke_check_stall): Perform stall checks against updated register
 	scheme.
	(pke_code_unpack): Correct operand-count calculation.
	(pke_code_stmask): Correct instruction skipping.

	* sky-pke.h (PKE_MEM_WRITE, PKE_MEM_READ): New kludge macros.
	(BIT_MASK_BTW): Corrected off-by-one error.
	(enum wordclass): Classify words in a FIFO quadword.

	* sky-dma.c (dma_io_read_buffer): Correct address checking assertions.

	* sky-engine.c (engine_run): Pass along SIM_DESC to PKE
 	instruction issue code.