Collaborative transaction building

Takes the dualopen collaborative transaction building and makes it available for other daemons to use

Changelog-Added: Added interactive transaction building routine

Author: ddustin

common/Makefile

@@ -43,6 +43,7 @@ COMMON_SRC_NOGEN :=				\
 	common/htlc_trim.c			\
 	common/htlc_tx.c			\
 	common/htlc_wire.c			\
+	common/interactivetx.c			\
 	common/initial_channel.c		\
 	common/initial_commit_tx.c		\
 	common/io_lock.c			\