The stack data is normally sliced from the actual script and btcscript is not
supposed to ever change the tx passed into it.
Add a test (and fix the other leading zeros tests) to stop this happening again.
PayToPubKeyHashScript generates a new pay to pubkey hash script to use
as the pkScript when creating new transactions. If the passed pubkey
hash is an invalid size, StackErrInvalidOpcode will be returned as an
error.
SignatureScript returns the signature script necessary to validate a
single input of a transaction.
This also adds sanity checking for serializing scripts into byte
slices. If the length of a serialized opcode does not equal the
expected length, StackErrInvalidOpcode will be returned when unparsing
a []parsedOpcode.
New internal tests were added to verify checks for valid and invalid
parsed opcodes.
Removing from the bottom of a stack (nipN(depth)) would leak the first
entry in the array by slicing [1:], leaving array[0] dangling an
inaccessible (but unable to be freed until the whole slice is gone). We
left it like this for a while, but best not to leak the memory. Happens
rarely so the performance hit shouldn't matter that much. Do the same
thing for condstack.
