Perl readline creates empty sys$command files if no STDIN is connected

This was originally reported to TortoiseGit: http://code.google.com/p/tortoisegit/issues/detail?id=1011

This patch was also reported to MinGW (http://sourceforge.net/p/mingw/patches/506/) and upstream perl (https://rt.perl.org//Public/Bug/Display.html?id=115900) where it was finally accepted and applied (to version 5.18).

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Merge pull request #152 from csware/syscommand

Perl readline creates empty sys$command files if no STDIN is connected