Fixed convert_octal()'s signature

There was a mismatch between int64_t and uint64_t, should be uint64_t
Fixed a bug with the pre-allocated PDT

My math was off and instead a better method was found to automatically
do it
Some of the math for the physical allocator was wrong

Fixed a bunch of math problems. Added invlpg support (not sure if
correct). Added a test to see if the physical allocator allocates
correct pages. Added some more definitions to the paging header.
Initial physical allocator and stack modules
Added a few more helper targets