* Create components for Rust and C integration
* Create component for C code that will be callable from Rust
* Create component for Rust code that will be callable from C
* Remove circular dependencies between C and Rust code
* Run cbindgen to dynamically generate C headers for Rust functions
* Add "std" feature to rustlib to allow using std in Xtensa projects
* Fix cargo target in CMakeLists.txt
* Use std feature when building for Xtensa
* Use std ffi aliases when building with std feature
* Add custom ffi aliases when building without std feature
* Add no_std attribute and panic handler when building without std feature
franchioping
Robert Cottrell
Ivan Grokhotkov
Juraj Michalek