rename "UVMHIST" option to enable the uvm histories.
TODO:
- make UVMHIST properly depend upon KERNHIST
- enable dynamic registration of histories. this is mostly just
allocating something in a bitmap, and is only for viewing multiple
histories in a merged form.
tested on amd64 and sparc64.
way they can be included without having to include DDB.
(arguably all print routines should be behind #ifdef DEBUGPRINT
and options DDB should define that macro, but I'll tackle that later)
use queue.h macros and KASSERT().
address amap offsets in pages instead of bytes.
make amap_ref() and amap_unref() take an amap, offset and length
instead of a vm_map_entry_t.
improve whitespace and comments.
