Include local functions in definition of async functions (#1393)

Author: jnm2

standard/classes.md

@@ -5391,7 +5391,7 @@ For a discussion of the behavior when an exception is thrown from a finalizer, s
 
 ### 15.14.1 General
 
-A method ([§15.6](classes.md#156-methods)) or anonymous function ([§12.19](expressions.md#1219-anonymous-function-expressions)) with the `async` modifier is called an ***async function***. In general, the term ***async*** is used to describe any kind of function that has the `async` modifier.
+A method ([§15.6](classes.md#156-methods)), anonymous function ([§12.19](expressions.md#1219-anonymous-function-expressions)), or local function ([§13.6.4](statements.md#1364-local-function-declarations)) with the `async` modifier is called an ***async function***. In general, the term ***async*** is used to describe any kind of function that has the `async` modifier.
 
 It is a compile-time error for the parameter list of an async function to specify any `in`, `out`, or `ref` parameters, or any parameter of a `ref struct` type.