Only use FileSpec if on Windows platform

In IO-CaptureOutput 1.1103, a change was made in wperl.t to require File::Spec 3.27. This change breaks the build process in Linux distributions which include an older version of File::Spec (for example, SUSE Linux Enterprise 11 includes version 3.2501).

As this is a Windows specific test, the 'use File::Spec 3.27' requirement can be moved behind an eval statement after the Windows platform check This allows the build process to work on Linux (without the File::Spec requirement), while still ensuring File::Spec 3.27 is required for Windows platforms.