Implement new StableApiDefinition VM control methods

[ianks]

In order to support Truffleruby on magnus, we need to support VM control operations, which currently relies on cruby internals.

/// Causes the interpreter to abort with a message. This function never
/// returns (akin to `rb_bug`).
///
/// **Important**: This function is an absolute last resort. It should
/// only be used if all else fails.
fn vm_panic(&self, message: &CStr) -> !;

/// Issues a warning using Ruby's `warn` function (akin to `rb_warning`).
fn vm_warning(msg: &CStr);