i'd like to remove the global counter hack from mod_ssl that only reads
the passphrase on the first module init.  currently does so because that
is the only time httpd is still attached to the tty, but if
SSLPassPhraseDialog is exec: rather than built in, a tty is not required
to read the passphrase.  but in the case of builtin, i need to know if
stdout is connected to a tty.  i'm guessing that isatty(fileno(stdout))
is not portable.  thinking we'll need something like:

apr_file_t *out;
apr_file_open_stdout(&out, pool);

if (apr_file_isatty(out)) { ... }

thoughts?