AP_Param: cope with older gcc versions

Travis-CI uses 4.6.3

libraries/AP_Param/AP_Param.cpp

@@ -1089,6 +1089,8 @@ void AP_Param::show_all(AP_HAL::BetterStream *port)
     }
 }
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat"
 // convert one old vehicle parameter to new object parameter
 void AP_Param::convert_old_parameter(const struct ConversionInfo *info)
 {
@@ -1116,10 +1118,7 @@ void AP_Param::convert_old_parameter(const struct ConversionInfo *info)
     AP_Param *ap2;
     ap2 = find_P((const prog_char_t *)&info->new_name[0], &ptype);
     if (ap2 == NULL) {
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wformat"
         hal.console->printf_P(PSTR("Unknown conversion '%S'\n"), info->new_name);
-#pragma GCC diagnostic pop
         return;
     }
 
@@ -1149,12 +1148,10 @@ void AP_Param::convert_old_parameter(const struct ConversionInfo *info)
         }
     } else {
         // can't do vector<->scalar conversion, or different vector types
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wformat"
         hal.console->printf_P(PSTR("Bad conversion type '%S'\n"), info->new_name);
-#pragma GCC diagnostic pop
     }
 }
+#pragma GCC diagnostic pop
 
 
 // convert old vehicle parameters to new object parametersv