Make waitvsync available on apple2

libsrc/apple2/waitvsync.s

@@ -3,11 +3,13 @@
 ;
 ; void waitvsync (void);
 ;
-        .ifdef  __APPLE2ENH__
-
         .export         _waitvsync
         .import         ostype
 
+        .ifndef  __APPLE2ENH__
+        .import         machinetype
+        .endif
+
         .include        "apple2.inc"
 
 _waitvsync:
@@ -15,18 +17,27 @@ _waitvsync:
         bmi     iigs            ; $8x
         bvs     iic             ; $4x
 
+        .ifndef  __APPLE2ENH__
+        bit     machinetype     ; IIe/enh?
+        bmi     :+
+
+        lda     #$FF            ; ][+ Unsupported
+        tax
+        rts
+        .endif
+
 :       bit     RDVBLBAR
         bpl     :-              ; Blanking
 :       bit     RDVBLBAR
         bmi     :-              ; Drawing
-        rts
+        bpl     out
 
         ; Apple IIgs TechNote #40, VBL Signal
 iigs:   bit     RDVBLBAR
         bmi     iigs            ; Blanking
 :       bit     RDVBLBAR
         bpl     :-              ; Drawing
-        rts
+        bmi     out
 
         ; Apple IIc TechNote #9, Detecting VBL
 iic:    php
@@ -42,6 +53,6 @@ iic:    php
         bit     DISVBL
 :       sta     IOUDISON        ; IIc Tech Ref Man: The firmware normally leaves IOUDIS on.
         plp
+out:    lda     #$00
+        tax
         rts
-
-        .endif                  ; __APPLE2ENH__