Adjusted current working directory initialization on Apple and Atari.

Moving __cwd from BSS into INITBSS does of course ;-) not only impact the CBM targets but all targets with disk I/O support.

Note: Code using `__cwd-1` may trigger an ld65 range error because __cwd may end up at the very begining of a segment. As far as I see this is an ld65 bug which I'm not try to fix - at least here.

libsrc/atari/initcwd.s

@@ -21,13 +21,13 @@
         sta     ICBLH,x
         jsr     CIOV
         bmi     oserr
-        ldx     #0              ; ATEOL -> \0
-:       lda     __cwd,x
-        inx
+        ldx     #$FF            ; ATEOL -> \0
+:       inx
+        lda     __cwd,x
         cmp     #ATEOL
         bne     :-
         lda     #0
-        sta     __cwd-1,x
+        sta     __cwd,x
 oserr:  rts
 
 .endproc