techmap: Support mapping to dynamic cell types

[povik]

Sample of use:

(* techmap_celltype="$lcu" *)
module _80_lcu_primitive(P, G, CI, CO);
	parameter WIDTH = 2;

	(* force_downto *)
	input wire [WIDTH-1:0] P;
	(* force_downto *)
	input wire [WIDTH-1:0] G;
	input wire CI;
	(* force_downto *)
	output wire [WIDTH-1:0] CO;

	(* techmap_chtype=$sformatf("LCU_%0d", WIDTH) *)
	_TECHMAP_PLACEHOLDER_ #(.WIDTH(WIDTH)) _TECHMAP_REPLACE_(.P(P), .G(G), .CI(CI), .CO(CO));
endmodule

to map $lcu cells to cells LCU_x where x is the width.

[widlarizer]

I assume you forgot to add this commit into the PR, it was only on the or-patches branch

[povik]

Yes, thanks