Provide assembly versions of the clock timing calculation loops that
aren't effected by changes in compiler optimisation.

Fixes PR port-mips/26959 from Izumi Tsutsui
correct the comment describing the build order
While processing soft interrupts, don't call splx()/lowerspl() when
unnecessary, as they call dosoftints().
Set -Wno-error on a per-source basis instead of the NOGCCERROR sledgehammer.
add cases for '040 and '060 FPUs.  from Radek Kujawa.
Make this compile again.
for in-kernel maps,
- allocate kva for vm_map_entry from the map itsself and
  remove the static limit, MAX_KMAPENT.
- keep merged entries for later splitting to fix allocate-to-free problem.
  PR/24039.
introduce vm_map_kernel, a subclass of vm_map, and
move some kernel-only members of vm_map to it.
introduce a new flag for pool_init, PR_NOTOUCH.
if it's specified, don't use free items as storage for internal state.
so that we can use pools for non memory backed objects.
inspired from solaris's KMC_NOTOUCH.
in the case of !PMAP_MAP_POOLPAGE, gather pool backend allocations to
large chunks for kernel_map and kmem_map to ease kva fragmentation.
PR_NOTOUCH:
- use uint8_t instead of uint16_t for freelist index.
- set ph_off only if PR_NOTOUCH.
- comment.
don't merge incompatible map entries.  eg. private and shared.
uvm_unmap_remove: debug check to ensure that
unmapped regions doesn't have any remaining page mappings.
sync with kernel.  (vm_map_entry::flags)
bump to 2.99.12.  uvm and pool changes.
bump version in a comment as well.
Add commented out pf and pflog pseudo-devices.
document PR_NOTOUCH and bump date.
add a linted comment.
Cosmetic: change u_int{8,16,32,64}_t to C99-style uint{8,16,32,64}_t,
which is preferred.