send-email: futureproof split_addrs() sub

Matt Kraai points out that calling parse_line() assuming that the caller
ever passes only one argument is a bug waiting to happen, and he is
right.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-send-email.perl

@@ -361,7 +361,7 @@ foreach my $entry (@bcclist) {
 }
 
 sub split_addrs {
-	return parse_line('\s*,\s*', 1, @_);
+	return quotewords('\s*,\s*', 1, @_);
 }
 
 my %aliases;