Add support for HIP15

include/blockchain_vars.hrl

@@ -179,6 +179,8 @@
 -define(poc_witnesses_percent, poc_witnesses_percent).
 -define(poc_challengers_percent, poc_challengers_percent).
 -define(dc_percent, dc_percent).
+-define(witness_redundancy, witness_redundancy).
+-define(poc_reward_decay_rate, poc_reward_decay_rate).
 
 %%%
 %%% bundle txn vars

src/transactions/v1/blockchain_txn_poc_receipts_v1.erl

@@ -774,7 +774,7 @@ absorb(Txn, Chain) ->
     catch What:Why:Stacktrace ->
               lager:error([{poc_id, POCID}], "poc receipt calculation failed: ~p ~p ~p",
                           [What, Why, Stacktrace]),
-            {error, state_missing}
+              {error, state_missing}
     end.
 
 -spec get_lower_and_upper_bounds(Secret :: binary(),

src/transactions/v1/blockchain_txn_vars_v1.erl

@@ -914,6 +914,10 @@ validate_var(?poc_challengers_percent, Value) ->
     validate_float(Value, "poc_challengers_percent", 0.0, 1.0);
 validate_var(?dc_percent, Value) ->
     validate_float(Value, "dc_percent", 0.0, 1.0);
+validate_var(?witness_redundancy, Value) ->
+    validate_int(Value, "witness_redundancy", 2, 100, false);
+validate_var(?poc_reward_decay_rate, Value) ->
+    validate_float(Value, "poc_reward_decay_rate", 0.0, 1.0);
 validate_var(?reward_version, Value) ->
     case Value of
         N when is_integer(N), N >= 1,  N =< 5 ->