Function p2wpkh_script_code 

pub fn p2wpkh_script_code(pubkey_hash: &[u8; 20]) -> Vec<u8> 

Build the BIP-143 script code for a P2WPKH input.

For P2WPKH, the script code is OP_DUP OP_HASH160 PUSH20(hash160) OP_EQUALVERIFY OP_CHECKSIG.