kernel - Expand the x86_64 KVA to 8G
* Our kmem_init() was mapping out the ~6G of KVA below KERNBASE. KERNBASE
is at the -2G mark and unlike i386 it does not mark the beginning of KVA.
Add two more globals, virtual2_start and virtual2_end, adn adjust
kmem_init() to use that space. This fixes kernel_map exhaustion issues
on x86_64. Before the change only ~600M of KVA was available after a
fresh boot.
* Populate the PDPs around both KERNBASE and at virtual2_start for
bootstrapping purposes.
* Adjust kernel_vm_end to start iteration for growkernel purposes at
VM_MIN_KERNEL_ADDRESS and no longer use it to figure out the end
of KVM for the minidump.
In addition, adjust minidump to dump the entire kernel virtual
address space.
* Remove numerous extranious variables.
* Fix a bug in vm_map_insert() where vm_map->first_free was being
incorrect set when the map does not begin with reserved space.