Implement paged memory

[netromdk]

Paged memory is important. Especially because I'm confined to using the stack until this has been implemented.

[netromdk]

Kernel:
Initially use a bitmap to store if each physical page is free or used, or use a stack. There can be a total of 4 GB pages where each page is 4 KB, so 1048576 pages. I will keep it simple at first but it should be considered later whether it'd be preferable to switch to a buddy allocation scheme.

1. Write a page frame allocator.
2. Implement virtual memory management.

libc++:
Typical std malloc()/new implementations use sbrk(value) to increment/decrement the amount of available memory and it would use actual kernel routines/syscalls to achieve this. But there are a lot of different ways of doing it.