Update libgit2 to 0.26

tiennou · tiennou · commit c39f10924612 · 2017-06-19T21:21:09.000+02:00
diff --git a/External/libgit2 b/External/libgit2
@@ -1 +1 @@
-Subproject commit 2fcb8705e584ca61f6c4657525c9d2713f6a39d2
+Subproject commit 15e119375018fba121cf58e02a9f17fe22df0df8
