MFC r205014,205015:

MFC r205014,205015:

Provide groundwork for 32-bit binary compatibility on non-x86 platforms,
for upcoming 64-bit PowerPC and MIPS support. This renames the COMPAT_IA32
option to COMPAT_FREEBSD32, removes some IA32-specific code from MI parts
of the kernel and enhances the freebsd32 compatibility code to support
big-endian platforms.

This MFC is required for MFCs of later changes to the freebsd32
compatibility from HEAD.

Requested by:	kib

git-svn-id: svn://svn.freebsd.org/base/stable/8@206336 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f