add create, does>, etc

core.fth

@@ -106,3 +106,13 @@
 : j         postpone 2r> ['] r> , postpone r@ ['] swap ,
             ['] >r , ['] -rot , postpone 2>r ; immediate
 
+: create    : here [ 4 cells ] literal + postpone literal postpone ; 0 , ;
+: >body     [ 2 cells ] literal + @ ;
+
+: _does>    latest dup cell+ @ [ 5 cells ] literal + +
+            ['] _jmp over ! cell+ ! ;
+
+: does>     here 4 cells + postpone literal ['] _does> , 0 , ; immediate
+
+: variable create cell allot ;
+: constant create , does> @ ;