Merge pull request #1153 from diffblue/past4

KNOWNBUG test for `$past` with hierarchical identifier

Author: tautschnig

regression/verilog/system-functions/past4.desc

@@ -0,0 +1,9 @@
+KNOWNBUG
+past4.sv
+
+^EXIT=10$
+^SIGNAL=0$
+--
+^warning: ignoring
+--
+$past doesn't allow the hierarchical identifier.

regression/verilog/system-functions/past4.sv

@@ -0,0 +1,10 @@
+module M;
+  wire x;
+endmodule
+
+module main(input clk);
+  M m();
+  
+  assert property (@(posedge clk) $past(m.x));
+  
+endmodule