Implemented Feature #60524 (system_tmp_dir)

Added a new configuration directive which allows it to change the
temporary directory, the default behavior is unchanged.

This is a useful option if you use all/some hosts inside of one .ini file
with sections and want to change the temp dir per user (maybe it's not
allowed to write outside the users home directory). Since the TMPDIR
variable affects the whole php that way can not be used for this scenario.

(see https://bugs.php.net/bug.php?id=60524)