Add test: 'Warning: ignoring initial value on non-register: \o'

tests/sat/initval.ys

@@ -2,3 +2,13 @@ read_verilog -sv initval.v
 proc;;
 
 sat -seq 10 -prove-asserts
+
+design -reset
+read_verilog -icells <<EOT
+module top(input clk, i, output o, p);
+(* init = 1'bx *)
+wire p = o;
+$_DFF_P_ dff (.C(clk), .D(i), .Q(o));
+endmodule
+EOT
+sat -seq 1