Under some conditions, geany_run_script.sh is not deleted and we
have no means to detect this in Geany (e.g. when the terminal emulator
is started correctly but it fails to execute the script for some reason).
In this case it is better to keep the garbage in /tmp than the working
directory. Apart from that, it eliminates potential transfer of the run script
over a NFS and eliminates the visibility of the script in working directory
on Windows.

Apart from that this patch fixes some locale/utf8 conversion problems
and other subtle problems with the previous implementation.