Correct the expected number of inputs for stake P2SH outputs
Correct the expected number of inputs for stake P2SH outputs

The required number of inputs for a stake P2SH output were incorrectly
estimated by CalcScriptInfo. Now the sub class for any given output is
also checked for whether or not it is P2SH.

decred/dcrd,jcmincke/dcrd,jcmincke/dcrd,jrick/dcrd,jrick/btcd,decred/dcrd,jrick/btcd,jrick/dcrd,jrick/btcd,jcmincke/dcrd