Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r232262 by tijl:

Copy amd64 _limits.h to x86 and merge with i386 _limits.h. Replace
amd64/i386/pc98 _limits.h with stubs.

MFC (part of) r235939 by obrien:

Consitently use "__LP64__".

Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add reach-over include files to read i386/foo.h. In time, the pc98
specific code will migrate to these files to augment or replace the
version in i386/include and/or i386/linux. This should, in the
fullness of time, allow many of the #ifdef PC98 in the tree.

# These files are in the public domain because there is insufficient
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OK'd in principle by: nyan@