[tex-k] Another quick fix

[Karl Berry]

    ssize_t is not in the C standard.  I'm not saying we shouldn't use it, but
    it might limit portability.  

A simple configure test could define it if need be. I suspect there is
no need.

    if we are limiting TeX to POSIX systems or not.

C vs. POSIX has never been a concern. There has been no effort to ensure
everything compiles on C-without-POSIX.

    My feeling is, if we fix any we likely should go through and fix them all

It's unclear to me that there is any "all".
In any case, I see no way to do it except one change at a time.

    (at least within one subproject like kpathsea),  

We're not talking about anything kpathsea here.

    testing process for all at once.

It's unclear to me that any "testing process" is feasible beyond "make
check". Certainly I'm not going to be sitting around dreaming up new
tests for each line of affected code, anyway ... --best, karl.