AP_Param: correct maximum-length parameter sanity check

need to take into account addition of (eg.) _X suffix for VECTOR3F parameters

Author: peterbarker

libraries/AP_Param/AP_Param.cpp

@@ -268,7 +268,12 @@ void AP_Param::check_group_info(const struct AP_Param::GroupInfo *  group_info,
         if (size == 0) {
             FATAL("invalid type in %s", group_info[i].name);
         }
-        if (prefix_length + strlen(group_info[i].name) > 16) {
+        uint8_t param_name_length = prefix_length + strlen(group_info[i].name);
+        if (type == AP_PARAM_VECTOR3F) {
+            // need room for _X/_Y/_Z
+            param_name_length += 2;
+        }
+        if (param_name_length > 16) {
             FATAL("suffix is too long in %s", group_info[i].name);
         }
         (*total_size) += size + sizeof(struct Param_header);