Bump ffi version since chef-dk depends on chef and dep-selector and dep-selector uses ~> 1.9.
Use FFI::LastError instead of GetLastError for ffi 1.9.x compatibility.
Fix windows specs.
Misc spec fixes for windows.
Merge pull request #1528 from opscode/sersut/bump-ffi-version

Bump ffi version since chef-dk depends on chef and dep-selector and dep-selector uses ~> 1.9.