svnimport: support repositories requiring SSL authentication

I looked at svn-mirror to see how it did this, seems about right.
"It works for me" when using it against https://svn.musicpd.org

tested command-line: git-svnimport -C mpc -i -m -v  \
	-T mpc/trunk -b mpc/branches -t mpc/tags https://svn.musicpd.org

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-svnimport.perl

@@ -96,8 +96,10 @@ sub new {
 sub conn {
 	my $self = shift;
 	my $repo = $self->{'fullrep'};
-	my $s = SVN::Ra->new($repo);
-
+	my $auth = SVN::Core::auth_open ([SVN::Client::get_simple_provider,
+			  SVN::Client::get_ssl_server_trust_file_provider,
+			  SVN::Client::get_username_provider]);
+	my $s = SVN::Ra->new(url => $repo, auth => $auth);
 	die "SVN connection to $repo: $!\n" unless defined $s;
 	$self->{'svn'} = $s;
 	$self->{'repo'} = $repo;