git-svn: fix segfaults due to initial SVN pool being cleared

Some parts of SVN always seem to use it, even if the SVN::Ra
object we're using is no longer used and we've created a new one
in its place.  It's also true that only one SVN::Ra connection
can exist at once...  Using SVN::Pool->new_default when the
SVN::Ra object is created doesn't seem to help very much,
either...

Hopefully this fixes all segfault problems users have been
experiencing over the past few months.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

git-svn.perl

@@ -2904,7 +2904,6 @@ sub new {
 	my ($class, $url) = @_;
 	$url =~ s!/+$!!;
 	return $RA if ($RA && $RA->{url} eq $url);
-	$RA->{pool}->clear if $RA;
 
 	SVN::_Core::svn_config_ensure($config_dir, undef);
 	my ($baton, $callbacks) = SVN::Core::auth_open_helper([