Make PM_NODE_FLAG_COMMON_MASK into a constant

Author: kddnewton

templates/include/prism/ast.h.erb

@@ -55,7 +55,7 @@ typedef uint16_t pm_node_flags_t;
 #define PM_NODE_FLAG_BITS (sizeof(pm_node_flags_t) * 8)
 static const pm_node_flags_t PM_NODE_FLAG_NEWLINE = (1 << (PM_NODE_FLAG_BITS - 1));
 static const pm_node_flags_t PM_NODE_FLAG_STATIC_LITERAL = (1 << (PM_NODE_FLAG_BITS - 2));
-static const pm_node_flags_t PM_NODE_FLAG_COMMON_MASK = PM_NODE_FLAG_NEWLINE | PM_NODE_FLAG_STATIC_LITERAL;
+static const pm_node_flags_t PM_NODE_FLAG_COMMON_MASK = (1 << (PM_NODE_FLAG_BITS - 1)) | (1 << (PM_NODE_FLAG_BITS - 2));
 
 // For easy access, we define some macros to check node type
 #define PM_NODE_TYPE(node) ((enum pm_node_type)node->type)