Update libgit2 to v0.25.1

pietbrauer · pietbrauer · commit e6abb591e357 · 2017-01-10T10:22:00.000+01:00
diff --git a/External/libgit2 b/External/libgit2
@@ -1 +1 @@
-Subproject commit 75db289a041b1f1084768244e167b953ac7eeaa5
+Subproject commit 2fcb8705e584ca61f6c4657525c9d2713f6a39d2
