Make PageTable repr(C)

We removed repr(transparent) in the last commit because it is not compatible with repr(align). However we should still keep PageTable FFI-safe, so this commit adds repr(C) to it.

Author: phil-opp

src/structures/paging/page_table.rs

@@ -170,6 +170,7 @@ const ENTRY_COUNT: usize = 512;
 /// This struct implements the `Index` and `IndexMut` traits, so the entries can be accessed
 /// through index operations. For example, `page_table[15]` returns the 15th page table entry.
 #[repr(align(4096))]
+#[repr(C)]
 pub struct PageTable {
     entries: [PageTableEntry; ENTRY_COUNT],
 }