ArduCopter Channel Config: config vars for user override of MOT_n mapping

* config variable CONFIG_CHANNELS has possible values
  CHANNEL_CONFIG_DEFAULT or CHANNEL_CONFIG_CUSTOM
* config_channels.h only provides APM1/APM2 mapping when
  CONFIG_CHANNELS == CHANNEL_CONFIG_DEFAULT

ArduCopter/config.h

@@ -188,6 +188,13 @@
 # define CONFIG_SONAR ENABLED
 #endif
 
+//////////////////////////////////////////////////////////////////////////////
+// Channel Config (custom MOT channel mappings)
+//
+
+#ifndef CONFIG_CHANNELS
+# define CONFIG_CHANNELS CHANNEL_CONFIG_DEFAULT
+#endif
 
 //////////////////////////////////////////////////////////////////////////////
 // Acrobatics

ArduCopter/config_channels.h

@@ -16,13 +16,15 @@
 //////////////////////////////////////////////////////////////////////////////
 //
 
-#include "config.h"
+#include "config.h"     // Parent Config File
+#include "APM_Config.h" // User Overrides
 
 //
 //
 // Output CH mapping for ArduCopter motor channels
 //
 //
+#if CONFIG_CHANNELS == CHANNEL_CONFIG_DEFAULT
 # if CONFIG_APM_HARDWARE == APM_HARDWARE_APM2
 #  define MOT_1 CH_1
 #  define MOT_2 CH_2
@@ -42,6 +44,7 @@
 #  define MOT_7 CH_10
 #  define MOT_8 CH_11
 # endif 
+#endif
 
 //
 //

ArduCopter/defines.h

@@ -369,4 +369,9 @@ enum gcs_severity {
 #define LOGGING_SIMPLE    1
 #define LOGGING_VERBOSE   2
 
+// Channel Config selection
+
+#define CHANNEL_CONFIG_DEFAULT 1
+#define CHANNEL_CONFIG_CUSTOM  2
+
 #endif // _DEFINES_H