Move IMMEDIATE from z80c to core

This makes IMMEDIATE affected by memory mappings.

forth/core.fs

@@ -1,5 +1,8 @@
 : H@ HERE @ ;
-: -^ SWAP - ;
+: IMMEDIATE
+    CURRENT @ 1 -
+    DUP C@ 128 OR SWAP C!
+;
 : [ INTERPRET 1 FLAGS ! ; IMMEDIATE
 : ] R> DROP ;
 : LIT 34 , ;
@@ -29,6 +32,7 @@
   (br)) and then call LITN on it. )
 
 : +! SWAP OVER @ + SWAP ! ;
+: -^ SWAP - ;
 : ALLOT HERE +! ;
 
 : IF                ( -- a | a: br cell addr )

forth/icore.fs

@@ -53,11 +53,7 @@
     '           ( get word )
     -^          ( apply offset )
     ,           ( write! )
-;
-( We can't use IMMEDIATE because the one we've just compiled
-  in z80c target's the *target*'s RAM addr, not the host's.
-  manually set namelen field. )
-0x82 CURRENT @ 1 - C!
+; IMMEDIATE
 
 : RAM+
     [ RAMSTART LITN ] _c +
@@ -250,9 +246,7 @@
 
 ( : and ; have to be defined last because it can't be
   executed now also, they can't have their real name
-  right away. We also can't use IMMEDIATE because the offset
-  used for CURRENT is the *target*'s RAM offset. we're still
-  on the host.
+  right away.
 )
 
 : X
@@ -269,17 +263,15 @@
     ( maybe number )
     ELSE _c (parse*) _c @ EXECUTE _c LITN THEN
     AGAIN
-;
+; IMMEDIATE
 
 : Y
     ['] EXIT _c ,
     _c R> _c DROP     ( exit : )
-;
+; IMMEDIATE
 
-( Give ":" and ";" their real name and make them IMMEDIATE )
-0x81 ' X 1 - _C!
+( Give ":" and ";" their real name )
 ':' ' X 4 - _C!
-0x81 ' Y 1 - _C!
 ';' ' Y 4 - _C!
 
 ( Add dummy entry. we use CREATE because (entry) is, at this

forth/z80c.fs

@@ -311,13 +311,6 @@ CODE R>
     HL PUSHqq,
 ;CODE
 
-CODE IMMEDIATE
-    ( CURRENT == RAM+2 )
-    RAMSTART 0x02 + LDHL(nn),
-    HL DECss,
-    7 (HL) SETbr,
-;CODE
-
 CODE IMMED?
     HL POPqq,
     chkPS,