Support GIT DLL

Signed-off-by: Frank Li <lznuaa@gmail.com>

diff --git a/ext/tgit b/ext/tgit
index e7c7ab5..6ee5d48 160000 (submodule)
--- a/ext/tgit
+++ b/ext/tgit
@@ -1 +1 @@
-Subproject commit e7c7ab5be4faa63f2278e7218078470a25fffd7d
+Subproject commit 6ee5d4821cd7cc7a057ab60bf1b57322fedf5b41