fix errno related underscores in all libsrc/*.s files

libsrc/atari/open.s

@@ -19,7 +19,7 @@
         .import findfreeiocb
         .import incsp4
         .import ldaxysp,addysp
-        .import __oserror
+        .import ___oserror
 .ifdef  UCASE_FILENAME
         .import ucase_fn
 .endif
@@ -37,7 +37,7 @@ parmok: jsr     findfreeiocb
         beq     iocbok          ; we found one
 
         lda     #<EMFILE        ; "too many open files"
-seterr: jsr     __directerrno
+seterr: jsr     ___directerrno
         jsr     incsp4          ; clean up stack
         lda     #$FF
         tax
@@ -150,11 +150,11 @@ finish: php
         jsr     CIOV            ; close IOCB again since open failed
         jsr     fddecusage      ; and decrement usage counter of fd
         lda     tmp3            ; put error code into A
-        jmp     __mappederrno
+        jmp     ___mappederrno
 
 ok:     lda     tmp2            ; get fd
         ldx     #0
-        stx     __oserror
+        stx     ___oserror
         rts
 
 .endproc