[clib 0.2.0] Use cargo metadata to help generating Rust bindings of C libraries

Three months ago, clib 0.1.0 was released. I got feedback and suggestions from @matclad. Then version 0.2.0 was on its way to provide better integration with potential external tools. First I tried metabuild but failed. I realized some mechanism of "reverse dependencies" should be introduced. After pals and inwelling was published, now it is time to release clib 0.2.0.

Welcome to give more feedback and suggestions: clib 0.2.0.