bitcoin-tx: fix build warnings
bitcoin-tx: fix build warnings

Cleans up a bunch of:
warning: missing braces around initializer for ‘const<anonymous struct>’

(cherry picked from commit 616c24307f4f18d7dbd603b5d9688904f2d74210)

reddcoin-project/reddcoin,reddcoin-project/reddcoin,reddcoin-project/reddcoin,reddcoin-project/reddcoin,reddcoin-project/reddcoin,reddcoin-project/reddcoin