Building for iOS
WIP: Traits reform
WIP: minor modifications
WIP: experiments continue
WIP: removing lifetime bound from txn traits
Renamed cursor lifetime
WIP: hacking a workaround over the strange LMDB bug
Updated to nightly
close brace
fail! -> panic!, deref resolution
Use mdb with older android support
Support android

Summary:
Update makefile to support ndk-build for mdb. Rustc can build for android target without much trouble already.

Test plan:
follow https://github.com/rust-lang/rust/wiki/Doc-building-for-android
cargo build --target=arm-linux-androideabi