This commit fixes some instances of uninitialized memory.
In addition, the bootstrap tables for x64 are moved around a bit,
in this awful game of placing stuff where it won't collide with grub.
This fixes issues where it did not fit into the first few MiB,
or that GRUB loaded it someplace weird.
The kernel heap is now also protected against growing into the
ramdisk and the kernel stack.
Jonas 'Sortie' Termansen