Create a interrupts::gdt submodule

src/interrupts/gdt.rs

@@ -0,0 +1,13 @@
+pub struct Gdt {
+    table: [u64; 8],
+    next_free: usize,
+}
+
+impl Gdt {
+    pub fn new() -> Gdt {
+        Gdt {
+            table: [0; 8],
+            next_free: 1,
+        }
+    }
+}