Revert "Removed unused member variable ReactionData.rxn_number"

This variable is used in some applications we build against
cantera.

This reverts commit 7d7b6dd39d12c2e2bdd2a9d2a959c0aee3c0c4c5.

include/cantera/kinetics/ReactionData.h

@@ -21,6 +21,7 @@ public:
         reactionType = ELEMENTARY_RXN;
         validate = false;
         number = 0;
+        rxn_number = 0;
         reversible = true;
         rateCoeffType = ARRHENIUS_REACTION_RATECOEFF_TYPE;
         falloffType = NONE;
@@ -43,6 +44,7 @@ public:
 
     bool validate;
     int number;
+    int rxn_number;
     std::vector<size_t> reactants;
     std::vector<size_t> products;
     vector_fp rorder;

src/kinetics/importKinetics.cpp

@@ -852,6 +852,7 @@ bool rxninfo::installReaction(int iRxn, const XML_Node& r, Kinetics& kin,
 
     rdata.equation = eqn;
     rdata.number = iRxn;
+    rdata.rxn_number = iRxn;
 
     // Read the rate coefficient data from the XML file. Trigger an
     // exception for negative A unless specifically authorized.