avr: added initial module to handle reed contacts.

Detects and reports opening and closing of a window/door.
Nexts step is to allow for external configuration (e.g. standard mode
with one reed contact versus multi-contact mode to detect tilting of a
window/door).

avr/modules/reed/0BUILD

@@ -0,0 +1,11 @@
+<?xml?>
+
+<gwbuild>
+
+  <extradist>
+    main.asm
+  </extradist>
+
+</gwbuild>
+
+