fix issue where getrawtransaction RPC call does not work

[erasmospunk]

The RPC call getrawtransaction does not work with some transactions (coinbase and coinstake txs) in an orphaned block.

For example the following orphaned block can be fetched via the RPC
getblock 45fb29047b0d93691029b5931bb78cba076c4ac9aa8310acd1620709f5582b60
but the first transaction
getrawtransaction dcb0597105107b8e9af2f851fc120a7ebc2ee544ac06c1689ea0f9aebfddc11e
fails
error: {"code":-5,"message":"No information available about transaction"}

This patch solves the issue.
Credits go also to @sigmike for coming up with a solution for the NuBits client.

[brossi]

We'll get this into the next release binary, but for now, it's available if you compile Peerunity from source. Thank you for submitting this, @erasmospunk