AP_SerialManager: unify singleton naming to _singleton and get_singleton()

libraries/AP_SerialManager/AP_SerialManager.cpp

@@ -226,12 +226,12 @@ const AP_Param::GroupInfo AP_SerialManager::var_info[] = {
 };
 
 // singleton instance
-AP_SerialManager *AP_SerialManager::_instance;
+AP_SerialManager *AP_SerialManager::_singleton;
 
 // Constructor
 AP_SerialManager::AP_SerialManager()
 {
-    _instance = this;
+    _singleton = this;
     // setup parameter defaults
     AP_Param::setup_object_defaults(this, var_info);
 }
@@ -555,7 +555,7 @@ namespace AP {
 
 AP_SerialManager &serialmanager()
 {
-    return *AP_SerialManager::get_instance();
+    return *AP_SerialManager::get_singleton();
 }
 
 }

libraries/AP_SerialManager/AP_SerialManager.h

@@ -109,8 +109,8 @@ public:
     };
 
     // get singleton instance
-    static AP_SerialManager *get_instance(void) {
-        return _instance;
+    static AP_SerialManager *get_singleton(void) {
+        return _singleton;
     }
     
     // init_console - initialise console at default baud rate
@@ -154,7 +154,7 @@ public:
     static const struct AP_Param::GroupInfo var_info[];
 
 private:
-    static AP_SerialManager *_instance;
+    static AP_SerialManager *_singleton;
     
     // array of uart info
     struct UARTState {