Fix bug #287: gyro correction ignored by autopilot

The generic-autopilot-helper computes heading-bug-error from
magnetic heading, not indicated heading. This patch corrects
this by pulling the two used generic helper filters into our
own config (so the generic-ap-helper.xml can go away).

Aircraft/c172p/Systems/KAP140.xml

@@ -5,6 +5,26 @@
 <!-- component. -->
 <PropertyList>
 
+  <filter>
+    <name>heading bug error computer/normalizer</name>
+    <debug>false</debug>
+    <type>gain</type>
+    <input>
+      <property>autopilot/settings/heading-bug-deg</property>
+      <offset>
+        <property>instrumentation/heading-indicator/indicated-heading-deg</property>
+        <scale>-1.0</scale>
+      </offset>
+    </input>
+    <output>autopilot/internal/heading-bug-error-deg</output>
+    <period>
+      <min>-180</min>
+      <max>180</max>
+    </period>
+    <gain>1.0</gain>
+  </filter>
+
+
   <!-- =============================================================== -->
   <!-- Roll Axis Modes                                                 -->
   <!-- =============================================================== -->
@@ -228,6 +248,15 @@
     </config>
    </pid-controller>
 
+  <filter>
+    <name>static port pressure rate computer</name>
+    <debug>false</debug>
+    <type>derivative</type>
+    <input>systems/static[0]/pressure-inhg</input>
+    <output>autopilot/internal/pressure-rate</output>
+    <filter-time>1.0</filter-time>
+  </filter>
+
    <filter>
     <name>pressure-rate-filter</name>
     <debug>false</debug>

Aircraft/c172p/c172p-set.xml

@@ -68,10 +68,6 @@ Started October 23 2001 by John Check, fgpanels@rockfish.net
   </view>
 
   <systems>
-    <autopilot>
-      <name>autopilot helpers</name>
-      <path>Aircraft/Generic/generic-autopilot-helper.xml</path>
-    </autopilot>
     <autopilot>
       <path>Aircraft/c172p/Systems/KAP140.xml</path>
     </autopilot>