Add ruby 2.1 to the list of cross build ruby versions for Windows.
Add ruby 2.1 to the list of cross build ruby versions for Windows.

MikaelSmith/ffi,majioa/ffi,sparkchaser/ffi,mvz/ffi,ferventcoder/ffi,mvz/ffi,MikaelSmith/ffi,sparkchaser/ffi,majioa/ffi,ferventcoder/ffi,yghannam/ffi,tduehr/ffi,yghannam/ffi,tduehr/ffi,yghannam/ffi,sparkchaser/ffi,majioa/ffi,ferventcoder/ffi,tduehr/ffi,yghannam/ffi,ffi/ffi,yghannam/ffi,sparkchaser/ffi,MikaelSmith/ffi,MikaelSmith/ffi,ffi/ffi,majioa/ffi,tduehr/ffi,ffi/ffi,mvz/ffi,ferventcoder/ffi,mvz/ffi