completion: complete values for send-email

completion: complete values for send-email

Add completion for --confirm, --suppress-cc, and --smtp-encryption
command line arguments. Add completion for aliasfiletype and confirm
configuration variables.

Since --smtp-ssl is deprecated, replace it with --smtp-encryption and
the two options ssl and tls.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>