unix98 says putenv() returns non-zero for errors - check for that rather than just negative values.
unix98 says putenv() returns non-zero for errors - check for that rather
than just negative values.

--HG--
branch : HEAD

jkerihuel/dovecot,dscho/dovecot,jwm/dovecot-notmuch,dscho/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,dscho/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,dscho/dovecot,jkerihuel/dovecot,dscho/dovecot,jkerihuel/dovecot