AP_Winch: stop libraries including AP_Logger.h in .h files

AP_Logger.h is a nexus of includes; while this is being improved over
time, there's no reason for the library headers to include AP_Logger.h
as the logger itself is access by singleton and the structures are in
LogStructure.h

This necessitated moving The PID_Info structure out of AP_Logger's
namespace.  This cleans up a pretty nasty bit - that structure is
definitely not simply used for logging, but also used to pass pid
information around to controllers!

There are a lot of patches in here because AP_Logger.h, acting as a
nexus, was providing transitive header file inclusion in many (some
unlikely!) places.

libraries/AP_Winch/AP_Winch.h

@@ -59,7 +59,7 @@ public:
     float get_rate_max() const { return MAX(config.rate_max, 0.0f); }
 
     // send status to ground station
-    void send_status(const GCS_MAVLINK &channel);
+    void send_status(const class GCS_MAVLINK &channel);
 
     // write log
     void write_log();

libraries/AP_Winch/AP_Winch_Backend.cpp

@@ -1,5 +1,7 @@
 #include <AP_Winch/AP_Winch_Backend.h>
+
 #include <RC_Channel/RC_Channel.h>
+#include <SRV_Channel/SRV_Channel.h>
 
 // setup rc input and output
 void AP_Winch_Backend::init()

libraries/AP_Winch/AP_Winch_Daiwa.cpp

@@ -1,4 +1,6 @@
 #include <AP_Winch/AP_Winch_Daiwa.h>
+
+#include <AP_Logger/AP_Logger.h>
 #include <GCS_MAVLink/GCS.h>
 
 extern const AP_HAL::HAL& hal;

libraries/AP_Winch/AP_Winch_PWM.cpp

@@ -1,4 +1,6 @@
 #include "AP_Winch_PWM.h"
+
+#include <AP_Logger/AP_Logger.h>
 #include <GCS_MAVLink/GCS.h>
 
 extern const AP_HAL::HAL& hal;