remove redundant nightly features

kernel/src/arch/x86_64/driver/vga.rs

@@ -1,15 +1,10 @@
-use core::ptr::Unique;
 use core::fmt;
 use spin::Mutex;
 use volatile::Volatile;
+use lazy_static::lazy_static;
 use x86_64::instructions::port::Port;
 use crate::logging::Color;
 use crate::consts::KERNEL_OFFSET;
-use lazy_static::lazy_static;
-
-pub const VGA_BUFFER: Unique<VgaBuffer> = unsafe {
-    Unique::new_unchecked((KERNEL_OFFSET + 0xb8000) as *mut _)
-};
 
 #[derive(Debug, Clone, Copy)]
 struct ColorCode(u8);
@@ -73,8 +68,7 @@ impl VgaBuffer {
 
 lazy_static! {
 	pub static ref VGA_WRITER: Mutex<VgaWriter> = Mutex::new(
-		// It is the only user of VGA_BUFFER. So it's safe.
-		VgaWriter::new(unsafe{ &mut *VGA_BUFFER.as_ptr() })
+		VgaWriter::new(unsafe{ &mut *((KERNEL_OFFSET + 0xb8000) as *mut VgaBuffer) })
 	);
 }
 

kernel/src/lib.rs

@@ -1,16 +1,10 @@
-#![feature(ptr_internals)]
 #![feature(lang_items)]
-#![feature(const_fn)]
 #![feature(alloc)]
 #![feature(naked_functions)]
 #![feature(asm)]
 #![feature(optin_builtin_traits)]
 #![feature(panic_info_message)]
 #![feature(global_asm)]
-#![feature(compiler_builtins_lib)]
-#![feature(raw)]
-#![feature(vec_resize_default)]
-#![feature(extern_crate_item_prelude)]
 #![no_std]
 
 // just keep it ...