z80: move back R* words to native words section

This allows us to refer to pushRS/popRS routines by labels, allowing
us to get rid of the pushRS reference in the stable ABI zone.

blk/282

@@ -1,2 +1,2 @@
-VARIABLE lblofl VARIABLE lblpushRS VARIABLE lblexec
-VARIABLE lblfind
+VARIABLE lblofl VARIABLE lblpushRS VARIABLE lblpopRS
+VARIABLE lblexec VARIABLE lblfind

blk/283

@@ -2,7 +2,7 @@ H@ ORG !
 0 JP, ( 00, main ) NOP, ( unused ) NOP, NOP, ( 04, BOOT )
 NOP, NOP, ( 06, uflw ) NOP, NOP, ( 08, LATEST )
 NOP, NOP, NOP, NOP, NOP, NOP, NOP, ( 0a, unused )
-0 JP, ( 11, pushRS ) 0 JP, ( 14, popRS )
+NOP, NOP, NOP, ( unused ) 0 JP, ( 14, popRS )
 NOP, NOP, NOP, ( unused )
 0 JP, ( 1a, next ) NOP, NOP, NOP, ( unused )
 NOP, NOP, NOP, NOP, ( unused )

blk/288

@@ -1,15 +0,0 @@
-CODE >R
-    HL POP, 17 BCALL, ( 17 == pushRS )
-;CODE
-CODE R>
-    20 BCALL, ( 20 == popRS ) HL PUSH,
-;CODE
-CODE 2>R ( 0xa9 )
-PC ORG @ 0x35 + ! ( stable ABI JP )
-    DE POP, HL POP,
-    17 BCALL, ( 17 == pushRS ) EXDEHL, 17 BCALL,
-;CODE NOP, NOP, NOP,
-CODE 2R>
-    20 BCALL, ( 20 == popRS ) EXDEHL, 20 BCALL,
-    HL PUSH, DE PUSH,
-;CODE

blk/297

@@ -1,10 +1,10 @@
-lblpushRS BSET PC ORG @ 0x12 + ! ( pushRS )
+lblpushRS BSET
     IX INCd, IX INCd,
     0 IX+ L LDIXYr,
     1 IX+ H LDIXYr,
     RET,
 
-PC ORG @ 0x15 + ! ( popRS )
+lblpopRS BSET PC ORG @ 0x15 + ! ( popRS )
     L 0 IX+ LDrIXY,
     H 1 IX+ LDrIXY,
     IX DECd, IX DECd,

blk/326

@@ -0,0 +1,15 @@
+CODE >R
+    HL POP, lblpushRS @ CALL,
+;CODE
+CODE R>
+    lblpopRS @ CALL, HL PUSH,
+;CODE
+CODE 2>R
+PC ORG @ 0x35 + ! ( stable ABI JP )
+    DE POP, HL POP,
+    lblpushRS @ CALL, EXDEHL, lblpushRS @ CALL,
+;CODE
+CODE 2R>
+    lblpopRS @ CALL, EXDEHL, lblpopRS @ CALL,
+    HL PUSH, DE PUSH,
+;CODE