message: Added upstream leveldb repo to submodules
diff: path = leveldb
  url = https://github.com/spectrecoin/leveldb.git
  branch = spectre
  +[submodule "leveldb_upstream"]
  + path = leveldb_upstream
  + url = https://github.com/google/leveldb.git
  + branch = master
  [submodule "db4.8"]
  path = db4.8
  url = https://github.com/spectrecoin/db4.8
  