z80: protect BC in _find

In preparation for the IY->BC move

blk/291

@@ -7,6 +7,7 @@ CODE _find  ( cur w -- a f )
     A (HL) LDrr, A ORr,
 	( special case. zero len? we never find anything. )
     IFZ, PUSH0, JPNEXT, THEN,
+    BC PUSH, ( --> lvl 2, protect )
 ( Let's do something weird: We'll hold HL by the *tail*.
   Because of our dict structure and because we know our
   lengths, it's easier to compare starting from the end. )

blk/292

@@ -1,7 +1,7 @@
     BEGIN, ( loop )
     ( DE is a wordref, first step, do our len correspond? )
-        HL PUSH, ( --> lvl 2 )
-        DE PUSH, ( --> lvl 3 )
+        HL PUSH, ( --> lvl 3 )
+        DE PUSH, ( --> lvl 4 )
         DE DECd,
         LDA(DE),
         0x7f ANDi, ( remove IMMEDIATE flag )

blk/294

@@ -1,13 +1,13 @@
 ( At this point, Z is set if we have a match. In all cases,
   we want to pop HL and DE )
-        DE POP, ( <-- lvl 3 )
+        DE POP, ( <-- lvl 4 )
         IFZ, ( match, we're done! )
-            HL POP, HL POP, ( <-- lvl 1-2 ) DE PUSH, PUSH1,
-            JPNEXT,
+            HL POP, BC POP, HL POP, ( <-- lvl 1-3 ) DE PUSH,
+            PUSH1, JPNEXT,
         THEN,
         ( no match, go to prev and continue )
         DE DECd, DE DECd, DE DECd, ( prev field )
-        DE PUSH, ( --> lvl 3 )
+        DE PUSH, ( --> lvl 4 )
         EXDEHL,
         LDDE(HL),
 

blk/295

@@ -1,13 +1,14 @@
         ( DE contains prev offset )
-        HL POP, ( <-- lvl 3, prev field )
+        HL POP, ( <-- lvl 4, prev field )
         DEZ, IFNZ, ( offset not zero )
             ( get absolute addr from offset )
             ( carry cleared from "or e" )
             DE SBCHLd,
             EXDEHL, ( result in DE )
         THEN,
-        HL POP, ( <-- lvl 2 )
+        HL POP, ( <-- lvl 3 )
     JRNZ, AGAIN, ( loop-B292, try to match again )
+    BC POP, ( <-- lvl 2 )
     ( Z set? end of dict, not found. "w" already on PSP TOS )
     PUSH0,
 ;CODE