portability

[Guy Harris]

> Does _flsbuf need to be rewritten to call __write() or
>something similar

Yes.

>where __write is implemented as:

No.  What I think AT&T plans to do for S5R4, for example, is to *rename*
the "write" routine "_write", and have a mechanism by which the linker
will let "_write" satisfy unresolved references for "write" (or
something like that); this means programs that call "write" and expect
it to be the "write" in the system library will not have to be changed -
but neither will programs that have their own private "write".

(Since "write" is usually implemented as a small assembly-language stub,
"syscall" doesn't enter into it.)