Makefiles: Update submodule reference to latestes for leveldb.

diff --git a/src/leveldb b/src/leveldb
index e9d7916ce652bfaed334106f4bf83f4d65f5c66e..ac2f95d3501233fb2a951760d16b77d7efb4dba2 160000 (submodule)
--- a/src/leveldb
+++ b/src/leveldb
@@ -1 +1 @@
-Subproject commit e9d7916ce652bfaed334106f4bf83f4d65f5c66e
+Subproject commit ac2f95d3501233fb2a951760d16b77d7efb4dba2