c-api: expose tail call configuration option in c api

[womeier]

The tail call proposal configuration is not yet exposed by the C api.
This change intends to allow configuring the option in e.g. the python library bindings:
bytecodealliance/wasmtime-py#204

I wanted to test this change doing the following:

Following the docs, I ran
cargo build --release --manifest-path crates/c-api/Cargo.toml which should place libwasmtime.{a,so} in target/release.
The command succeeded, but the file is not generated (and I cannot find libwasmtime.so with find).

I thus didn't test the change further than the fact that it compiles, in particular I didn't yet test the change
with the python library.
Tested to work together with the PR: bytecodealliance/wasmtime-py#205 adjusting the python bindings.

[alexcrichton]

Looks great to me, thanks! Apologies for the documentation but it's outdated. Nowadays the correct invocation is with -p wasmtime-c-api instead of --manifest-path .... I'll send a separate PR to update those docs.

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[womeier]

Thanks for the quick response @alexcrichton!

I created a PR with the changes to the python bindings, they work as expected together, i.e. I can run my wasm module with tail calls using the python lib :)