If requested, actually treat uncomfirmed change as being uncomfirmed

This commit strengthens 1bbca249b202c4802cc2c4d4de4a26e6392b4d92 by updating the CWalletTx::IsConfirmed() function.

If (bSpendZeroConfChange==false), then IsConfirmed() should actually treat unconfirmed change as being unconfirmed.
Rename IsConfirmed to IsTrusted to better match the intended behavior.

This doesn't change the functionality at all.
Merge pull request #3657

fdbc2b1 If requested, actually treat uncomfirmed change as being uncomfirmed (b6393ce9-d324-4fe1-996b-acf82dbc3d53)
Add raw transaction hex to `gettransaction` wallet RPC

This allows getting raw transaction data from the wallet even if the
transaction is no longer in the blockchain / mempool (for example if it
got orphaned due to malleability abuse).
Merge pull request #3668

3a1c20b Add raw transaction hex to `gettransaction` wallet RPC (Wladimir J. van der Laan)
Merge pull request #3662

0542619 Rename IsConfirmed to IsTrusted to better match the intended behavior. (Gregory Maxwell)