This package uses the (La)TeX extension -shell-escape to
establish whether the document is being processed on a Windows
or on a Unix-like system (Mac OS X, Linux, etc.), or on Cygwin
(Unix environment over a windows system). Booleans provided
are: \ifwindows, \iflinux, \ifmacosx and \ifcygwin. The package
also preserves the output of uname on a Unix-like system, which
may be used to distinguish between various classes of Unix
systems.
