Modules that provide OS-specific behaviors often need to know if the
current operating system matches a more generic type of operating
systems. For example, 'linux' is a type of 'Unix' operating system and
so is 'freebsd'.
This module provides a mapping between an operating system name as given
by $^O and a more generic type. The initial version is based on the OS
type mappings provided in Module::Build and ExtUtils::CBuilder. (Thus,
Microsoft operating systems are given the type 'Windows' rather than
'Win32'.)
