use documented IIGS detection, fixes FastChip issues

src/4cade.init.a

@@ -40,11 +40,13 @@
 @no64Klen=(*-@s_no64K)-1
 
 +        jsr   DisableAccelerator    ; set to 1 MHz (supports IIgs and many common accelerator cards)
-         jsr   IsGS                  ; check for IIgs (allows super hi-res artwork)
-         php
-         bcc   +
+         sec
+         jsr   $FE1F                 ; check for IIgs (allows super hi-res artwork)
+         bcs   NotGS
          jsr   ROM_TEXT2COPY         ; set alternate display mode on IIgs (required for some games)
-+        plp
++        sec
+         +HIDE_NEXT_BYTE
+NotGS    clc
          ror   zpMachineStatus
          sta   SETC3ROM
          jsr   HasVidHDCard          ; check for VidHD card (allows super hi-res artwork even on non-IIgs machines)
@@ -145,7 +147,6 @@
 ProRWTSBuffer
          ; these routines will only be called once, from main memory, before relocating to language card
          !source "src/hw.diskcheck.a"
-         !source "src/hw.iigs.a"
          !source "src/hw.vidhd.a"
          !source "src/hw.memcheck.a"
          !source "src/hw.joystick.a"

src/hw.iigs.a

@@ -1,26 +0,0 @@
-;license:MIT
-;(c) 2018-9 by 4am
-;
-; IIgs support functions
-;
-
-;------------------------------------------------------------------------------
-; IsGS
-; detect IIgs by running CPU-specific magic
-;
-; in:    none
-; out:   C set if running on a IIgs
-;        C clear otherwise
-;        A clobbered
-;        X/Y preserved
-;------------------------------------------------------------------------------
-IsGS
-         lda   #0                    ; set Z flag
-!cpu 65816
-         rep   #2                    ; clear Z flag on 65816 only
-!cpu 6502
-         beq   @no
-@yes     sec
-         +HIDE_NEXT_BYTE
-@no      clc
-         rts