Function emit_bigint_alu_verilog 

pub fn emit_bigint_alu_verilog() -> String

Emit the 256-bit add / subtract / compare datapath. The {cout,sum} / {borrow,diff} use a 257-bit context so the carry / borrow out of the top limb is captured; lt is the borrow (a < b ⇔ the subtract underflows), eq the magnitude equality.