(PE-3180) win32-security SID buffer size too small

 - When calling `Windows::Security::SID.new('foo')`, the SID of user `'foo'`
   is looked up with the Win32 API call `LookupAccountSid`.  Unfortunately
   the `win32-security` gem hardcodes a fixed size buffer which is too
   small for the returned SID under certain circumstances (for domain
   SIDs for instance).  Idiomatic Win32 API states that the first API
   call should be used to determine a buffer size, a buffer should then
   be allocated, and then a subsequent call should be made to the Win32
   API with the appropriate buffer.
 - Being 'more correct' would be a larger code change, so instead the
   simplest approach here is to bump up the buffer size appropriately.
 - Note that the version of `win32-security` we're presently using is
   > 1 year old, and we do have plans to replace it with a safer 0.2.5+
   version that uses FFI and follows safer practices around calling
   Win32 APIs.  However, at this time, this requires some more
   involved code changes that may be too large for a bugfix release.