Signal documentation

doc/lang/module.md

@@ -64,6 +64,9 @@ module to be executed, its signals have to be bound the
 caller signals in its scope (the scope of the corresponding
 `run` form).
 
+Within a module, the `in`, `out`, and `inout` signals can be used
+as any [local signals](./signal.md).
+
 For instance, the `M1` module can be used in the following
 `run` statement from a `M2` module.
 

doc/lang/signal.md

@@ -77,6 +77,12 @@ hiphop module M() {
 }
 ```
 
+[Module signals](./module.md) are declared with the keywords `in`,
+`out`, and `inout`.  The signals can be used from outside of the
+machine to pass values in or to receive values after a reaction.
+
+These are signals 
+
 ★ Example: [samelocalname.hh.js](../../test/samelocalname.hh.js)
 
 Signals can only be emitted once per instant, unless they are declared