add __rvalue(expression) builtin

Author: WalterBright

compiler/src/dmd/tokens.d

@@ -55,6 +55,7 @@ enum TOK : ubyte
     typeof_,
     pragma_,
     typeid_,
+    rvalue,
     comment,
 
     // Operators
@@ -314,6 +315,7 @@ enum EXP : ubyte
     declaration,
     dSymbol,
     typeid_,
+    rvalue,
     uadd,
     remove,
     newAnonymousClass,
@@ -460,6 +462,7 @@ private immutable TOK[] keywords =
     TOK.pragma_,
     TOK.typeof_,
     TOK.typeid_,
+    TOK.rvalue,
     TOK.template_,
     TOK.void_,
     TOK.int8,
@@ -680,6 +683,7 @@ extern (C++) struct Token
         TOK.pragma_: "pragma",
         TOK.typeof_: "typeof",
         TOK.typeid_: "typeid",
+        TOK.rvalue: "__rvalue",
         TOK.template_: "template",
         TOK.void_: "void",
         TOK.int8: "byte",