BIP-383: fix output scripts

[dr-orlovsky]

The output scripts given in the specification are invalid for the bitcoin OP_CHECKMULTISIG.

The operator must be preceded with a push of the total number of keys - see https://bitcoin.stackexchange.com/questions/40669/checkmultisig-a-worked-out-example and https://en.bitcoin.it/wiki/OP_CHECKMULTISIG for the details.

[jonatack]

cc BIP authors @achow101 @sipa for feedback

[achow101]

This is k and n is greater than 16

[achow101]

The script is indeed incorrect and this does fix it.

However, perhaps instead of exhaustively listing the possible k and n values when greater/less than 16, maybe reword it something like "k and n must be minimally encoded, i.e. values less than or equal to 16 are encoded with OP_0 through OP_16, while values greater than 16 are as a push of the signed little endian value with no leading 0's".