The generated context selectors now have the `Snafu` suffix.

The old interface was deprecated in version 3.0.0.

The methods used before were deprecated in the new version of the `config` crate.

The `get_str` method on `Config` struct was renamed to `get_string`.

Aside, the minimum Rust compiler version supported is now 1.49.0.

From `snafu-upgrade-assistant`:
In SNAFU 0.7, generated context selectors now have the Snafu suffix to help de-mystify the generated code.

From SNAFU's Changelog:
- Generated context selectors now have the suffix Snafu. This is a breaking change.
- Minimum supported version of Rust is now 1.34.

Remove the `volatile` crate in favor of the
`std::ptr::{read,write}_volatile` functions.

Also add `Cargo.lock` for `libtapasco_tests`.

Feature: Reintroduce `tapasco-debug` with new interface in Rust

Replace unnecessary `StatefulList`s with `ListStates`.
Make the number of registers and the size of local memory endless.

TryInto is now in the prelude of the 2021 edition.

that are necessary for `tapasco-debug` but break up the usually wanted
encapsulation of `libtapasco`, so they are guarded behind conditional
compilation if the non-default feature is activated.

Write the 1 to start the PE directly to the appropriate address in
the mapped memory. Using `libtapasco`'s API function to start a PE
is not possible because ownership of the `PE` struct has already
been taken and cannot be stolen back in the starting function.