Add msys to the list of unsupported systems

Windows "msys" installations don't seem to have a getgrouplist implementation
Fix getgrouplist for Cygwin

The cygwin implementation of getgrouplist will return the number of groups of
a user even if the group array is too small (or null); this differs from
the behavior of the linux call, where the return value in that case is -1.

Use a retval > 0 check for cygwin (and keep the < 0 relation for other cases).
Explicitly enable prototypes

Newer perl versions print warnings if the prototyping behavior (en-/disable)
is not configured explicitly.

Using PROTOTYPES: ENABLE fixes the warnings, and provides for a fine perl
prototype.
Adapt test 01 for cygwin environment

Test 01-getgrouplist-for-root.t checked whether user "root" belongs to group
0 (root as well). This obviously is not the case in Cygwin environments, where
user root does not exist. However, there's an "Administrator" with a uid of 500.

This commit checks user root if uid 0 exists, and tries the username of uid 500
otherwise.

This should still be valid for unix/linux, but also work with Cygwin.

A new test 02 was added that checks that the code does not crash for a
non-existing user ("barfuser").
Bump to v1.1.1