logging macros are moved out to the separate crate `log`.
Rust update: `libextra` is deleted. `extra::url` has moved out to a separate library
Merge pull request #66 from Kroisse/liblog

Logging macros are moved out to the separate crate `log`.
Merge pull request #65 from amesee/rust-update-libextra-url

`libextra` is deleted. `extra::url` has moved out to a separate library.