Add VPI examples

examples/log2-vpi/vpi_log2.sv

@@ -0,0 +1,22 @@
+`timescale 1ps/1ps
+
+`include "utest.vh"
+
+module vpi_log2 #(parameter ARGUMENT = 1.0,
+                  parameter SIGMA = 1e-6);
+    real dut, gold;
+
+    initial begin
+        gold = $ln(ARGUMENT) / $ln(2);
+        dut  = $log2(ARGUMENT);
+
+        `log_info(("Gold: %0f", gold));
+        `log_info((" DUT: %0f", dut));
+
+        if ($abs(gold - dut) > SIGMA)
+          `log_error(("FAIL"));
+
+        $finish;
+    end
+
+endmodule // vpi_log2