util: Do BlackBox Async Set/Reset Registers more properly (#305)

* util: Do Set/Reset Async Registers more properly

The way BlackBox "init" registers were coded before was
not really kosher verilog for most synthesis tools.
Also, the enable logic wasn't really pushed down into the flop.

This change is more explicit about set/reset flops,
again this is only a 'temporary' problem that would go away
with parameterizable blackboxes (or general async reset support).

* Tabs, not spaces, in Makefiles

* util: Fix typos in Async BB Reg Comments

vsim/Makefrag

@@ -8,10 +8,11 @@ bb_vsrcs = $(base_dir)/vsrc/DebugTransportModuleJtag.v \
 	$(base_dir)/vsrc/jtag_vpi.v \
 	$(base_dir)/vsrc/AsyncMailbox.v \
 	$(base_dir)/vsrc/AsyncResetReg.v \
+	$(base_dir)/vsrc/AsyncSetReg.v \
 	$(base_dir)/vsrc/ClockDivider.v \
-        $(base_dir)/vsrc/ClockToSignal.v \
-        $(base_dir)/vsrc/SignalToClock.v \
-        
+	$(base_dir)/vsrc/ClockToSignal.v \
+	$(base_dir)/vsrc/SignalToClock.v \
+
 
 sim_vsrcs = \
 	$(generated_dir)/$(MODEL).$(CONFIG).v \