Adding latch tests for shift&mask AST dynamic part-select enhancements

tests/various/dynamic_part_select/latch_002.v

@@ -0,0 +1,13 @@
+`default_nettype none
+module latch_002
+  (dword, sel, st, vect);
+   output reg [63:0] dword;
+   input wire [7:0]  vect;
+   input wire [7:0]  sel;
+   input wire        st;
+   
+   always @(*) begin
+      if (st)
+	dword[8*sel +:8] <= vect[7:0];
+   end
+endmodule // latch_002