The introduction email (--compose option) have encoding hardcoded to
UTF-8, but invoked editor may not use UTF-8 encoding.
The encoding used by patches can be changed by the "8bit-encoding"
option, but this option does not have effect on introduction email
and equivalent for introduction email is missing.
Added compose-encoding command line option and sendemail.composeencoding
configuration option specify encoding of introduction email.
Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>