76c4c647cf Reexport `Magic` (Martin Habovstiak)
Pull request description:
Writing `network::Magic` is more natural and less annoying than `network::constants::Magic`, so this change reexports it.
Closes#1667
ACKs for top commit:
apoelstra:
ACK 76c4c647cf
tcharding:
ACK 76c4c647cf
Tree-SHA512: 1d85372ecd9723c0871faa4552ba5f93a3c95d0b213fa8aace398949f97157cdfde164bbcb2c35bae4c61ae0185e3fbdb854714cde0849c1afaf90e4e8ec223f