Kernel: Enable the x86 WP bit to catch invalid memory writes in ring 0

Setting this bit will cause the CPU to generate a page fault when
writing to read-only memory, even if we're executing in the kernel.

Seemingly the only change needed to make this work was to have the
inode-backed page fault handler use a temporary mapping for writing
the read-from-disk data into the newly-allocated physical page.

Kernel/VM/MemoryManager.cpp

@@ -174,7 +174,7 @@ void MemoryManager::initialize_paging()
     asm volatile("movl %%eax, %%cr3" ::"a"(kernel_page_directory().cr3()));
     asm volatile(
         "movl %%cr0, %%eax\n"
-        "orl $0x80000001, %%eax\n"
+        "orl $0x80010001, %%eax\n"
         "movl %%eax, %%cr0\n" ::
             : "%eax", "memory");