Allow unlimited line length in fpm config files

Fixes bug [#65933](https://bugs.php.net/bug.php?id=65933)

[Ref. for this actually causing a problem in the real world](http://serverfault.com/questions/547394/is-there-a-limit-setting-a-php-admin-value-in-php-fpm)
AFAICT `buf[n++] = '\0';` would work here, instead of having `memset()` all over.