Add support for the Host Power State feature. (#1772)

* Add support for the Host Power State feature.

* Fix compiler ewrrors.

* Fix compiler errors round 2.

* Add newlines to end of file.

* Address review comments.

* Arrange to send the power state response again if the first attempt fails.

* Fix compiler issue.

examples/drivers/windows/otCli/main.cpp

@@ -32,6 +32,7 @@
 #include <openthread/openthread.h>
 #include <openthread/cli.h>
 #include <openthread/platform/uart.h>
+#include <openthread/platform/misc.h>
 
 bool skipNextLine = false;
 
@@ -83,3 +84,8 @@ EXTERN_C ThreadError otPlatUartSend(const uint8_t *aBuf, uint16_t aBufLength)
 
     return error;
 }
+
+EXTERN_C void otPlatWakeHost(void)
+{
+
+}