move findfreeiocb function into its own object file

libsrc/atari/fdtable.s

@@ -11,7 +11,6 @@
         .import fdt_to_fdi
         .export clriocb
         .export fdtoiocb_down
-        .export findfreeiocb
         .export fddecusage
         .export newfd
 
@@ -87,31 +86,6 @@ loop:   sta     ICHID,x
 .endproc
 
 
-; find a free iocb
-; no entry parameters
-; return ZF = 0/1 for not found/found
-;        index in X if found
-; all registers destroyed
-
-.proc   findfreeiocb
-
-        ldx     #0
-        ldy     #$FF
-loop:   tya
-        cmp     ICHID,x
-        beq     found
-        txa
-        clc
-        adc     #$10
-        tax
-        cmp     #$80
-        bcc     loop
-        inx                     ; return ZF cleared
-found:  rts
-
-.endproc        ; findfreeiocb
-
-
 ; decrements usage counter for fd
 ; if 0 reached, it's marked as unused
 ; get fd index in tmp2

libsrc/atari/findfreeiocb.inc

@@ -0,0 +1,23 @@
+; find a free iocb
+; no entry parameters
+; return ZF = 0/1 for not found/found
+;        index in X if found
+; all registers destroyed
+
+.proc   findfreeiocb
+
+        ldx     #0
+        ldy     #$FF
+loop:   tya
+        cmp     ICHID,x
+        beq     found
+        txa
+        clc
+        adc     #$10
+        tax
+        cmp     #$80
+        bcc     loop
+        inx                     ; return ZF cleared
+found:  rts
+
+.endproc        ; findfreeiocb

libsrc/atari/findfreeiocb.s

@@ -0,0 +1,7 @@
+;
+; Christian Groessler, June-2013
+;
+
+        .include "atari.inc"
+        .export findfreeiocb
+        .include "findfreeiocb.inc"