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

OK'ed by:	core

any fake value.

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

Approved by: core, peter, alc, rwatson

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

things over floppy size limits, I can exclude it for release builds or
something like that.  Most of the changes are to get the load_elf.c file
into a seperate elf32_ or elf64_ namespace so that you can have two
ELF loaders present at once.  Note that for 64 bit kernels, it actually
starts up the kernel already in 64 bit mode with paging enabled.  This
is really easy because we have a known minimum feature set.

Of note is that for amd64, we have to pass in the bios int 15 0xe821
memory map because once in long mode, you absolutely cannot make VM86
calls.  amd64 does not use 'struct bootinfo' at all.  It is a pure loader
metadata startup, just like sparc64 and powerpc.  Much of the
infrastructure to support this was adapted from sparc64.

Don't include <sys/disklabel.h>

Move the remaining bits of <sys/diskslice.h> to <i386/include/bootinfo.h>

Move i386/pc98 specific bits from <sys/reboot.h> to
<i386/include/bootinfo.h> as well.

Adjust includes in sys/boot accordingly.