send-email: Change from Mail::Sendmail to Net::SMTP
send-email: Change from Mail::Sendmail to Net::SMTP

Net::SMTP is in the base Perl distribution, so users are more
likely to have it.  Net::SMTP also allows reusing the SMTP
connection, so sending multiple emails is faster.

[jc: tweaked X-Mailer further while we are at it.]

Signed-off-by: Eric Wong <8c2951295f8292b0c03727bc4652981172298eae@yhbt.net>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

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