Update libgit2 to (almost) 0.27.0-rc1

tiennou · tiennou · commit 3cdd4e62a4a5 · 2018-02-15T15:38:17.000+01:00
diff --git a/External/libgit2 b/External/libgit2
@@ -1 +1 @@
-Subproject commit 4f4bc5732baf4545ab42bbd80d2a971e2f1e316c
+Subproject commit b8cb75361d48f16f41dfa99b5b988a914e53040b
