Fix a warning pointed by GCC 7.1

lua_tonumber overflow in snprintf (12 bytes and only 10 can be written)

src/script/cpp_api/s_base.cpp

@@ -240,7 +240,7 @@ void ScriptApiBase::stackDump(std::ostream &o)
 				break;
 			case LUA_TNUMBER:  /* numbers */ {
 				char buf[10];
-				snprintf(buf, 10, "%g", lua_tonumber(m_luastack, i));
+				snprintf(buf, 10, "%lf", lua_tonumber(m_luastack, i));
 				o << buf;
 				break;
 			}