AC_PID: 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/AC_PID/AC_PID.h

@@ -7,7 +7,6 @@
 #include <AP_Param/AP_Param.h>
 #include <stdlib.h>
 #include <cmath>
-#include <AP_Logger/AP_Logger.h>
 #include <Filter/SlewLimiter.h>
 
 #define AC_PID_TFILT_HZ_DEFAULT  0.0f   // default input filter frequency
@@ -15,6 +14,8 @@
 #define AC_PID_DFILT_HZ_DEFAULT  20.0f   // default input filter frequency
 #define AC_PID_RESET_TC          0.16f   // Time constant for integrator reset decay to zero
 
+#include "AP_PIDInfo.h"
+
 /// @class	AC_PID
 /// @brief	Copter PID control class
 class AC_PID {
@@ -116,7 +117,7 @@ public:
     // return current slew rate of slew limiter. Will return 0 if SMAX is zero
     float get_slew_rate(void) const { return _slew_limiter.get_slew_rate(); }
 
-    const AP_Logger::PID_Info& get_pid_info(void) const { return _pid_info; }
+    const AP_PIDInfo& get_pid_info(void) const { return _pid_info; }
 
     // parameter var table
     static const struct AP_Param::GroupInfo var_info[];
@@ -155,5 +156,5 @@ protected:
     float _derivative;        // derivative value to enable filtering
     int8_t _slew_limit_scale;
 
-    AP_Logger::PID_Info _pid_info;
+    AP_PIDInfo _pid_info;
 };

libraries/AC_PID/AC_PID_2D.h

@@ -7,7 +7,7 @@
 #include <AP_Param/AP_Param.h>
 #include <stdlib.h>
 #include <cmath>
-#include <AP_Logger/AP_Logger.h>
+#include <AC_PID/AP_PIDInfo.h>
 
 /// @class	AC_PID_2D
 /// @brief	Copter PID control class
@@ -75,8 +75,8 @@ public:
     void set_integrator(const Vector3f& i) { set_integrator(Vector2f{i.x, i.y}); }
     void set_integrator(const Vector2f& i);
 
-    const AP_Logger::PID_Info& get_pid_info_x(void) const { return _pid_info_x; }
-    const AP_Logger::PID_Info& get_pid_info_y(void) const { return _pid_info_y; }
+    const AP_PIDInfo& get_pid_info_x(void) const { return _pid_info_x; }
+    const AP_PIDInfo& get_pid_info_y(void) const { return _pid_info_y; }
 
     // parameter var table
     static const struct AP_Param::GroupInfo        var_info[];
@@ -100,6 +100,6 @@ protected:
     Vector2f    _integrator;    // integrator value
     bool        _reset_filter;  // true when input filter should be reset during next call to update_all
 
-    AP_Logger::PID_Info _pid_info_x;
-    AP_Logger::PID_Info _pid_info_y;
+    AP_PIDInfo _pid_info_x;
+    AP_PIDInfo _pid_info_y;
 };

libraries/AC_PID/AC_PID_Basic.h

@@ -5,7 +5,7 @@
 
 #include <AP_Common/AP_Common.h>
 #include <AP_Param/AP_Param.h>
-#include <AP_Logger/AP_Logger.h>
+#include "AP_PIDInfo.h"
 
 /// @class	AC_PID_Basic
 /// @brief	Copter PID control class
@@ -70,7 +70,7 @@ public:
     void set_integrator(float error, float i);
     void set_integrator(float i);
 
-    const AP_Logger::PID_Info& get_pid_info(void) const WARN_IF_UNUSED { return _pid_info; }
+    const AP_PIDInfo& get_pid_info(void) const WARN_IF_UNUSED { return _pid_info; }
 
     // parameter var table
     static const struct AP_Param::GroupInfo var_info[];
@@ -94,5 +94,5 @@ protected:
     float _integrator;  // integrator value
     bool _reset_filter; // true when input filter should be reset during next call to set_input
 
-    AP_Logger::PID_Info _pid_info;
+    AP_PIDInfo _pid_info;
 };

libraries/AC_PID/AP_PIDInfo.h

@@ -0,0 +1,20 @@
+#pragma once
+
+// This structure provides information on the internal member data of
+// a PID.  It provides an abstract way to pass PID information around,
+// useful for logging and sending mavlink messages.
+
+// It is also used to pass PID information into controllers...
+
+struct AP_PIDInfo {
+    float target;
+    float actual;
+    float error;
+    float P;
+    float I;
+    float D;
+    float FF;
+    float Dmod;
+    float slew_rate;
+    bool  limit;
+};