[auth.h auth2.c auth2-hostbased.c auth2-kbdint.c auth2-none.c
auth2-passwd.c auth2-pubkey.c Makefile.in]
split auth2.c into one file per method; ok provos@/deraadt@
NOTE: Merged back noticable cygwin and pam stuff. May need review to
ensure I did not miss anything.