Add words "'S" and "S0"

blk/046

@@ -9,8 +9,8 @@ SWAP        a b -- b a
 2DUP        a b -- a b a b
 2OVER       a b c d -- a b c d a b
 2SWAP       a b c d -- c d a b
-PICK        Pick nth item from stack. "0 PICK" = DUP,
-            "1 PICK" = OVER.
-ROLL        Rotate PSP over n items. "1 ROLL" = SWAP,
-            "2 ROLL" = ROT. 0 is noop.
-
+'S          Returns current stack pointer, not counting the
+            push it's making right now.
+S0          Returns address of PSP TOS. When PSP is empty,
+            'S == S0
+                                                        (cont.)

blk/047

@@ -0,0 +1,7 @@
+(cont.)
+PICK        Pick nth item from stack. "0 PICK" = DUP,
+            "1 PICK" = OVER.
+ROLL        Rotate PSP over n items. "1 ROLL" = SWAP,
+            "2 ROLL" = ROT. 0 is noop.
+
+

forth/boot.z80

@@ -433,6 +433,17 @@ CODE 2DROP
     chkPS,
 ;CODE
 
+CODE S0
+    RAMSTART LDHL(nn), ( RAM+00 == INITIAL_SP )
+    HL PUSHqq,
+;CODE
+
+CODE 'S
+    HL 0 LDddnn,
+    SP ADDHLss,
+    HL PUSHqq,
+;CODE
+
 CODE AND
     HL POPqq,
     DE POPqq,