Revert "move enum to pair.h"

This reverts commit aebc8ea8.

src/pair.cpp

@@ -43,6 +43,8 @@
 using namespace LAMMPS_NS;
 using namespace MathConst;
 
+enum{NONE,RLINEAR,RSQ,BMP};
+
 // allocate space for static class instance variable and initialize it
 
 int Pair::instance_total = 0;

src/pair.h

@@ -32,8 +32,6 @@ class Pair : protected Pointers {
   friend class Info;
 
  public:
-  enum{NONE,RLINEAR,RSQ,BMP};
-
   static int instance_total;     // # of Pair classes ever instantiated
 
   double eng_vdwl,eng_coul;      // accumulated energies