'RELENG_7_0_0_RELEASE'.

This commit was manufactured to restore the state of the 7.0-RELEASE image.

cr0-4, etc.  Support should be added for other platforms that have a
different set of registers for system use.

Loosely based on: OpenBSD
Approved by:	re

Default off due to information disclosure on multi-user systems.

Submitted by:	cperciva
Reviewed by:	jhb

place.

This moves the dependency on GCC's and other compiler's features into
the central sys/cdefs.h file, while the individual source files can
then refer to #ifdef __COMPILER_FEATURE_FOO where they by now used to
refer to #if __GNUC__ > 3.1415 && __BARC__ <= 42.

By now, GCC and ICC (the Intel compiler) have been actively tested on
IA32 platforms by netchild.  Extension to other compilers is supposed
to be possible, of course.

Submitted by:	netchild
Reviewed by:	various developers on arch@, some time ago

license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

it belongs. Change the implementation to match those of rfs() and
rgs() for consistency and irrespective of whether the original was
more correct or not (technically speaking).

to build the kernel. It doesn't affect the operation if gcc.

Most of the changes are just adding __INTEL_COMPILER to #ifdef's, as
icc v8 may define __GNUC__ some parts may look strange but are
necessary.

Additional changes:
 - in_cksum.[ch]:
   * use a generic C version instead of the assembly version in the !gcc
     case (ASM code breaks with the optimizations icc does)
     -> no bad checksums with an icc compiled kernel
     Help from:		andre, grehan, das
     Stolen from: 	alpha version via ppc version
     The entire checksum code should IMHO be replaced with the DragonFly
     version (because it isn't guaranteed future revisions of gcc will
     include similar optimizations) as in:
        ---snip---
          Revision  Changes    Path
          1.12      +1 -0      src/sys/conf/files.i386
          1.4       +142 -558  src/sys/i386/i386/in_cksum.c
          1.5       +33 -69    src/sys/i386/include/in_cksum.h
          1.5       +2 -0      src/sys/netinet/igmp.c
          1.6       +0 -1      src/sys/netinet/in.h
          1.6       +2 -0      src/sys/netinet/ip_icmp.c

          1.4       +3 -4      src/contrib/ipfilter/ip_compat.h
          1.3       +1 -2      src/sbin/natd/icmp.c
          1.4       +0 -1      src/sbin/natd/natd.c
          1.48      +1 -0      src/sys/conf/files
          1.2       +0 -1      src/sys/conf/files.amd64
          1.13      +0 -1      src/sys/conf/files.i386
          1.5       +0 -1      src/sys/conf/files.pc98
          1.7       +1 -1      src/sys/contrib/ipfilter/netinet/fil.c
          1.10      +2 -3      src/sys/contrib/ipfilter/netinet/ip_compat.h
          1.10      +1 -1      src/sys/contrib/ipfilter/netinet/ip_fil.c
          1.7       +1 -1      src/sys/dev/netif/txp/if_txp.c
          1.7       +1 -1      src/sys/net/ip_mroute/ip_mroute.c
          1.7       +1 -2      src/sys/net/ipfw/ip_fw2.c
          1.6       +1 -2      src/sys/netinet/igmp.c
          1.4       +158 -116  src/sys/netinet/in_cksum.c
          1.6       +1 -1      src/sys/netinet/ip_gre.c
          1.7       +1 -2      src/sys/netinet/ip_icmp.c
          1.10      +1 -1      src/sys/netinet/ip_input.c
          1.10      +1 -2      src/sys/netinet/ip_output.c
          1.13      +1 -2      src/sys/netinet/tcp_input.c
          1.9       +1 -2      src/sys/netinet/tcp_output.c
          1.10      +1 -1      src/sys/netinet/tcp_subr.c
          1.10      +1 -1      src/sys/netinet/tcp_syncache.c
          1.9       +1 -2      src/sys/netinet/udp_usrreq.c

          1.5       +1 -2      src/sys/netinet6/ipsec.c
          1.5       +1 -2      src/sys/netproto/ipsec/ipsec.c
          1.5       +1 -1      src/sys/netproto/ipsec/ipsec_input.c
          1.4       +1 -2      src/sys/netproto/ipsec/ipsec_output.c

          and finally remove
            sys/i386/i386        in_cksum.c
            sys/i386/include     in_cksum.h
        ---snip---
 - endian.h:
   * DTRT in C++ mode
 - quad.h:
   * we don't use gcc v1 anymore, remove support for it
   Suggested by:	bde (long ago)
 - assym.h:
   * avoid zero-length arrays (remove dependency on a gcc specific
     feature)
     This change changes the contents of the object file, but as it's
     only used to generate some values for a header, and the generator
     knows how to handle this, there's no impact in the gcc case.
   Explained by:	bde
   Submitted by:	Marius Strobl <marius@alchemy.franken.de>
 - aicasm.c:
   * minor change to teach it about the way icc spells "-nostdinc"
   Not approved by:	gibbs (no reply to my mail)
 - bump __FreeBSD_version (lang/icc needs to know about the changes)

Incarnations of this patch survive gcc compiles since a loooong time,
I use it on my desktop. An icc compiled kernel works since Nov. 2003
(exceptions: snd_* if used as modules), it survives a build of the
entire ports collection with icc.

Parts of this commit contains suggestions or submissions from
Marius Strobl <marius@alchemy.franken.de>.

Reviewed by:	-arch
Submitted by:	netchild

in the non-_KERNEL case.  This "fixes" applications that include
this "kernel-only" header and also include <strings.h> (or get
<strings.h> via the default _BSD_VISIBLE pollution in <string.h>.
In C++ there was a fatal error: the declaration specifies C linkage
but the implementation gives C++ linkage.  In C there was only a
static/extern mismatch if the headers were included in a certain order
order, and a partially redundant declaration for all include orders;
gcc emits incomplete or wrong diagnostics for these, but only for
compiling with -Wsystem-headers and certain other warning options, so
the problem was usually not seen for C.

Ports breakage reported by:	kris

- completely unused things
- all of rev.1.102 (C++ support).  <sys/cdefs.h> is included by the
  prerequisite <sys/types.h>.  __BEGIN_DECLS/__END_DECLS has no effect
  (except possibly if undefined behaviour is invoked using a hack like
  defining away __inline) since this header doesn't really support any
  extern functions.