Add the needed defines for CDDL code

These are enough to build the libraries.
Update to build msun for arm64

 * The long double type on arm64 is quad-precision
 * Add fenv.c to export the required symbols
 * Fix _fpmath.h to be the correct size and pull out the correct bits

_fpmath.h is now based on the arm version.
Add the start of libkvm

This adds the needed stub functions to build it. They will be implemented
later when we have kernel core dumping support but are needed now to build
a few tools.
Add the definition of Elf32_Auxinfo

This lets us build libprocstat
Split lists of files to 1 per line to make merging easier
Add initial support for the threading libraries

Untested but will help world to be built.
Marker change. Above needs reviewing, below is on arm64-dev.

No need to review this change, it's only here to show which
changes are in arm64-dev vs abtsys.
Fix pmap_invalidate_range to always invalidate

Dynamic libraries need this.

While here ass sched_pin/sched_unpin calls around the invalidation
functions. These will be needed when we have SMP to ensure we don't
get moved to a different core during the invalidation process.
Clean up setjmp:

 * __longjmp appears to be for linuxthreads, we can bring in the fix
   later if needed.
 * Add a magic value to the start of the buffer to tell which function
   created it.
 * Use this value for siglongjmp.
 * Backup x1 in longjmp when calling sigprocmask as we need it later.
 * Fix typos in <machine/setjmp.h>
Allow shell scripts to work

They exposed a problem with pmap where anything run from them could
attempt to access the wrong physical page. This adds extra tlb
invalidation and moves one call before the unlock.

There is still a bug where, if the call to pmap_invalidate_all is removed
from pmap_alloc_l3 it will still crash, however I haven't managed to
track down why this is the case, even after adding invalidation to all
placed the l3 tables are changed.
Implment signal support

This adds the needed kernel changes to support signals.
Add brk and sbrk

A few things need these to build.
Add the last two simplefs ops
Update csu to use data passed to it by rtld
Don't add an empty item to the start of the map
Rename a few local variables

So they are differnt to the global variable in the same file.
Always copy the dtb to what will be a kernel address

It was only copied if it was loaded from a filesystem.