Merge rust-bitcoin/rust-bitcoin#802: Subsidy halving interval

94dd57d Add subsidy halving interval constant (Casey Rodarmor)

Pull request description:

  Fixes #801.

ACKs for top commit:
  Kixunil:
    ACK 94dd57d
  apoelstra:
    ACK 94dd57d

Tree-SHA512: e43df8888216017c1f9af4565890fad344c2822a8a11d5ae6453c300240a14ae89ce6b5d2a4bbdfb105f87606421accd7ecf42149d36442ffba05e3af94bdaa7

Author: apoelstra

src/blockdata/constants.rs

@@ -61,7 +61,8 @@ pub const PUBKEY_ADDRESS_PREFIX_TEST: u8 = 111; // 0x6f
 pub const SCRIPT_ADDRESS_PREFIX_TEST: u8 = 196; // 0xc4
 /// The maximum allowed script size.
 pub const MAX_SCRIPT_ELEMENT_SIZE: usize = 520;
-
+/// How may blocks between halvings.
+pub const SUBSIDY_HALVING_INTERVAL: u32 = 210_000;
 
 /// In Bitcoind this is insanely described as ~((u256)0 >> 32)
 pub fn max_target(_: Network) -> Uint256 {