metadata: Support "renamed" dependencies
    
    For example,
    
    ```toml
    [dependencies]
    open-ssl = { version="0.10", package = "openssl", optional = true }
    [features]
    openssl = ["actix-tls/openssl", "awc/openssl", "open-ssl"]
    ```
    
    would end up previously with just +openssl subpackage with dependency on
    crate(openssl). Now we create +open-ssl subpackage with dependency on
    crate(openssl) and +openssl subpackage with dependencies on
    crate(actix-tls/openssl), crate(awc/openssl) and +open-ssl subpackage.
    
    Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>