Paper over a race in DoubleBuffer.

I'm still somewhat okay throwing InterruptDisabler at races as they screw me.
Eventually I'm gonna have to devise a different strategy though.

Kernel/kmalloc.cpp

@@ -90,7 +90,7 @@ void* kmalloc_page_aligned(size_t size)
     return ptr;
 }
 
-void* kmalloc(dword size)
+void* kmalloc_impl(dword size)
 {
     InterruptDisabler disabler;