Remove leveldb in preparation for git-subtree
Squashed 'src/leveldb/' content from commit aca1ffc

git-subtree-dir: src/leveldb
git-subtree-split: aca1ffc4b65be5e099b2088c6e6a308d69e1ad73
Merge commit 'c25e98186d0f716451ef000e55646d25e014f573' as 'src/leveldb'
Merge pull request #2616 from vinniefalco/leveldb-as-subtree

Leveldb as subtree