chore: remove unused features

src/lib.rs

@@ -1,5 +1,4 @@
 #![allow(
-    mutable_transmutes,
     non_camel_case_types,
     non_snake_case,
     non_upper_case_globals,
@@ -7,12 +6,7 @@
     non_camel_case_types,
     non_snake_case
 )]
-#![feature(
-    c_variadic,
-    const_raw_ptr_to_usize_cast,
-    extern_types,
-    ptr_wrapping_offset_from
-)]
+#![feature(c_variadic, ptr_wrapping_offset_from)]
 
 #[macro_use]
 extern crate num_derive;