add support for != conditionals (#894)

* Accept `tok::ne` for conditional expressions in modcc, and emit correctly as '!=' in `cexpr_emit`.

modcc/expression.cpp

@@ -1133,6 +1133,7 @@ expression_ptr binary_expression(Location loc,
             return make_expression<PowBinaryExpression>(
                 loc, std::move(lhs), std::move(rhs)
             );
+        case tok::ne       :
         case tok::lt       :
         case tok::lte      :
         case tok::gt       :

modcc/printer/cexpr_emit.cpp

@@ -96,6 +96,7 @@ void CExprEmitter::visit(BinaryExpression* e) {
         {tok::gt,       ">"},
         {tok::gte,      ">="},
         {tok::equality, "=="},
+        {tok::ne,       "!="},
         {tok::min,      "min"},
         {tok::max,      "max"},
     };