Create inspect introspection functions for asyncgen.

```py
ASYNCGEN_CREATED = 'ASYNCGEN_CREATED'
ASYNCGEN_RUNNING = 'ASYNCGEN_RUNNING'
ASYNCGEN_SUSPENDED = 'ASYNCGEN_SUSPENDED'
ASYNCGEN_CLOSED = 'ASYNCGEN_CLOSED'

def getasyncgeneratorstate(asyncgenerator):
    """Get current state of a async generator-iterator.

    Possible states are:
      ASYNCGEN_CREATED: Waiting to start execution.
      ASYNCGEN_RUNNING: Currently being executed by the interpreter.
      ASYNCGEN_SUSPENDED: Currently suspended at a yield expression.
      ASYNCGEN_CLOSED: Execution has completed.
    """
    if asyncgenerator.ag_running:
        return ASYNCGEN_RUNNING
    if asyncgenerator.ag_frame is None:
        return ASYNCGEN_CLOSED
    if asyncgenerator.ag_frame.f_lasti == -1:
        return ASYNCGEN_CREATED
    return ASYNCGEN_SUSPENDED


def getasyncgeneratorlocals(asyncgenerator):
    """
    Get the mapping of async generator local variables to their current values.

    A dict is returned, with the keys the local variable names and values the
    bound values."""

    if not isasyncgen(asyncgenerator):
        raise TypeError("{!r} is not a Python generator".format(asyncgenerator))

    frame = getattr(asyncgenerator, "ag_frame", None)
    if frame is not None:
        return asyncgenerator.ag_frame.f_locals
    else:
        return {}
```

Seems to be duplicate of https://bugs.python.org/issue35759