Based on the Rust clippy lint that recommends that any public
function that dereferences a raw pointer, mark all FFI functions
that reference raw pointers with build_slice and cast_pointer
as unsafe.
This commits starts by removing the unsafe wrapper inside
the build_slice and cast_pointer macros then marks all
functions that use these macros as unsafe.
Then fix all not_unsafe_ptr_arg_deref warnings from clippy.
Fixes clippy lint:
https://rust-lang.github.io/rust-clippy/master/index.html#not_unsafe_ptr_arg_deref
All cases of our transmute can be replaced with more idiomatic
solutions and do no require the power of transmute.
When returning an object to C for life-time management, use
Box::into_raw to convert the boxed object to pointer and use
Box::from_raw to convert back.
For cases where we're just returning a pointer to Rust managed
data, use a cast.