kernel/isa: Remove empty isa_init() (formerly used for COMPAT_OLDISA).
kernel/x86_64: Remove some bogus #ifndefs.
libkern: Stop compiling in (u)cmpdi2.c, because they are not used.

It's 32 bit code that assumes that two longs fit into 64 bits,
hence put it into i386 'files' (commented out).
<malloc.h>: Restrict support for <malloc.h> to !defined(__STDC__).

In essence this is what FreeBSD did: error if __STDC__ is defined, and
silently include <stdlib.h> if not.

Packages are expected to now fail their config checks for <malloc.h>
but to build nevertheless, which was confirmed with building ~500
packages as a test.

Adjust a few config.h files of contrib/ code as well, notably
libssp's, which gets rid of the malloc.h warnings from the buildworld
output.
kernel - Implementat much deeper use of shared VM object locks

* Use a shared VM object lock on terminal (and likely highly shared)
  OBJT_VNODE objects.  For example, binaries in the system such as
  /bin/sh or /usr/bin/make.

  This greatly improves fork/exec and related VM faults on concurrently
  executing binaries.  Most commonly, parallel builds often exec
  hundreds of thousands of sh's and make's.

  +50% to +100% nominal improved performance under these conditions.
  +200% to +300% improved poudriere performance during the depend
  stage.

* Formalize the shared VM object lock with a new API function,
  vm_object_lock_maybe_shared(), which determines whether a VM
  object meets the requirements for obtaining a shared lock.

* Adjust the vm_fault*() APIs to track whether the VM object is
  locked shared or exclusive on entry.

* Clarify that OBJ_ONEMAPPING is only applicable to OBJT_DEFAULT
  and OBJT_SWAP objects.

* Heavy work on the exec path.  Somewhat lighter work on the exit
  path.  Tons more work could be done.
kernel - Separate page activity heuristic for anonymous memory vs files

* Add sysctls vm.anonmem_decline and vm.filemem_decline with reasonable
  defaults.

* Should improve retention of anonymous memory over file cache.
kernel - Track slabs allocated and freed

* Add statistics counters kern.slabs_allocated and kern.slabs_freed,
  tracking kernel memory allocator slab statistics.
kernel - Clean up if_bridge bif_state tests

* bif_state is only valid when IFBIF_STP is set, adjust two bits of
  code that were using bif_state unconditionally.

* This is a semi-operational change because bif_state's default value
  when IFBIF_STP is not set resulted in correct operation anyway.

  However, setting STP and then clearing it on a sub-interface could
  cause problems with stale state.
debug - vmpageinfo changes

* Adjust vmpageinfo to print more information.