* Introduce a `TargetFrontendConfig` type.
`TargetFrontendConfig` is information specific to the target which is
provided to frontends to allow them to produce Cranelift IR for the
target. Currently this includes the pointer size and the default calling
convention.
The default calling convention is now inferred from the target, rather
than being a setting. cranelift-native is now just a provider of target
information, rather than also being a provider of settings, which gives
it a clearer role.
And instead of having cranelift-frontend routines require the whole
`TargetIsa`, just require the `TargetFrontendConfig`, and add a way to
get the `TargetFrontendConfig` from a `Module`.
Fixes#529.
Fixes#555.
* Remove `Module`'s `finalize_function` and `finalize_data`.
Remove the ability to finalize individiual functions and data objects,
and instead just provide a way to finalize everything that's been
defined but not yet finalized. This allows SimpleJIT to share an
allocation between multiple functions without having to worry about
individual functions being finalized and needing to be published
without the other functions in the same allocation.
Users of the return values of `Module`'s `finalize_function` and
`finalize_data` should now use `get_finalized_function` and
`get_finalized_data` to obtain these values.
