send-email: visually distinguish sendmail aliases parser warnings
send-email: visually distinguish sendmail aliases parser warnings

Although emitted to stderr, warnings from the sendmail aliases parser
are not visually distinguished as such, and thus can easily be
overlooked in the normal noisy send-email output.

Signed-off-by: Eric Sunshine <8d6e34f987851aa599257d3831a1af040886842f@sunshineco.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git