Add $size() function. At the moment it works only on expressions, not on memories.

tests/simple/functions01.sv

@@ -0,0 +1,15 @@
+module functions01;
+wire [3:0]x;
+wire [$size(x)-1:0]x_size;
+wire [$size({x, x})-1:0]xx_size;
+wire [3:0]w[0:5];
+
+//
+// The following are not supported yet:
+//
+
+//wire [$size(w)-1:0]w_s;
+//wire [$bits(x)-1:0]x_bits;
+//wire [$bits({x, x})-1:0]xx_bits;
+
+endmodule