Created bare CR test input

Summary:
Fixes T17

Added cr2crlf function that reads a file descriptor and converts \n to \r\n

Thanks to msk@ for the code that I stole (line 3533 of libopendkim/dkim.c )

Test Plan: run make test

Maniphest Tasks: T17

Differential Revision: http://code.peteftw.com/D17