Fix task_handle type mismatch on task spawn

[agerasev]

freertos_rs_spawn_task from shim.c (as well as xTaskCreate) takes TaskHandle_t * as last argument.

But in shim.rs this function takes FreeRtosMutTaskHandle (*mut CVoid) which is not the same as *mut FreeRtosTaskHandle (*mut *const CVoid).

So xTaskCreate tries to store TaskHandle_t into CVoid, but they may have different size and alignment.

This PR fixes this issue.

[agerasev]

And also a question: why not to use core::ffi::c_void rather than create custom CVoid?

[schteve]

Good catch, it seems like this only worked so far because likely the CVoid size matches the pointer size in many cases.

As to the question of why CVoid, I don't have any answer. It looks like the implementation of core::ffi::c_void is similar to what was done here with two-variant enum. Maybe there is an opportunity to use the standard type.

[agerasev]

As to the question of why CVoid, I don't have any answer. It looks like the implementation of core::ffi::c_void is similar to what was done here with two-variant enum. Maybe there is an opportunity to use the standard type.

Ok, thanks, I'll try to switch to core::ffi::c_void and open a separate PR.

[agerasev]

Ok, thanks, I'll try to switch to core::ffi::c_void and open a separate PR.

Opened: #55

[schteve]

Thanks!