Extract Git::SVN::GlobSpec from git-svn.

Straight cut & paste.  That's the last class.

* Make Git::SVN load it on its own, its the only thing that needs it.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
diff --git a/perl/Git/SVN.pm b/perl/Git/SVN.pm
index 2e0d7f0..b8b3474 100644
--- a/perl/Git/SVN.pm
+++ b/perl/Git/SVN.pm
@@ -207,6 +207,8 @@
 			    . "must start with 'refs/'\n")
 				unless $remote_ref =~ m{^refs/};
 			$local_ref = uri_decode($local_ref);
+
+			require Git::SVN::GlobSpec;
 			my $rs = {
 			    t => $t,
 			    remote => $remote,