Crate capi

These are helper methods for building C APIs that have "alloc" and "free" methods to handle memory allocation of Rust objects.

The pair of methods to_c_owned() and to_owned_from_c() allows passing ownership of a Rust object to C and back.

You can create a Rust object and pass it to C with to_c_owned(), and you don't need to keep the reference to the object anywhere in the Rust part of the program.

Any object given to C via to_c_owned() has to be claimed back via to_owned_from_c(). You need to create a C function for deallocation of objects that then calls to_owned_from_c().

Objects owned by C can be borrowed back to the Rust land by using &T as extern "C"'s function type. If, for some reason, you declare functions to take a pointer you can get a reference via as_ref_from_c(), but this should usually be unneccessary.

mut and const versions of methods are only for convenience and are interchangeable.

Traits

FromCOwned	Takes ownership back from C. The pointer must not be used after to_owned_from_c() is called.
ToCOwned	Takes a Box and returns a C pointer that can be given to a C program to use for as long as it wants.