Fix for running PHP under CGI on Windows machines.  In this situation, the environement variables defining the system temp path are not necessarily available to PHP, so sys_get_temp_dir() falls back to using the system path (e.g. C:\WINDOWS), which is normally unwritable.  This means that temp-file creation fails.

I've added code to detect this situation, and if it occurs we point it to %SystemRoot%\TEMP instead, which usually is present and writable.  May not fix 100% of cases, but should fix the vast majority of situations where this may occur.
Merge pull request #15 from MarkMaldaba/windows_tempfolder_fix

Looks good to me.