ansi.h include guards

[coypu%sdf.org@localhost]

Hi folks

trying to make gcc work for netbsd/arm it turned out that gcc is relying
on the choice of include guards:
https://github.com/gcc-mirror/gcc/blob/master/gcc/ginclude/stddef.h#L59-L65

(if there is a better way to do it please mention..)

we haven't been very consistent in a per arch manner:

$ grep -H ifndef sys/arch/*/include/ansi.h
sys/arch/alpha/include/ansi.h:#ifndef   _ANSI_H_
sys/arch/amd64/include/ansi.h:#ifndef   _X86_64_ANSI_H_
sys/arch/amiga/include/ansi.h:#ifndef _MACHINE_ANSI_H_
sys/arch/arm/include/ansi.h:#ifndef _ARM_ANSI_H_
sys/arch/atari/include/ansi.h:#ifndef _MACHINE_ANSI_H_
sys/arch/dreamcast/include/ansi.h:#ifndef _DREAMCAST_ANSI_H_
sys/arch/evbsh3/include/ansi.h:#ifndef _EVBSH3_ANSI_H_
sys/arch/hpcsh/include/ansi.h:#ifndef _HPCSH_ANSI_H_
sys/arch/hppa/include/ansi.h:#ifndef    _ANSI_H_
sys/arch/i386/include/ansi.h:#ifndef    _I386_ANSI_H_
sys/arch/ia64/include/ansi.h:#ifndef    _ANSI_H_
sys/arch/landisk/include/ansi.h:#ifndef _LANDISK_ANSI_H_
sys/arch/m68k/include/ansi.h:#ifndef    _ANSI_H_
sys/arch/mips/include/ansi.h:#ifndef    _ANSI_H_
sys/arch/mips/include/ansi.h:#ifndef __mips_o32
sys/arch/powerpc/include/ansi.h:#ifndef _ANSI_H_
sys/arch/sh3/include/ansi.h:#ifndef     _ANSI_H_
sys/arch/sparc/include/ansi.h:#ifndef   _ANSI_H_
sys/arch/sparc64/include/ansi.h:#ifndef _ANSI_H_
sys/arch/usermode/include/ansi.h:#ifndef _ARCH_USERMODE_INCLUDE_ANSI_H
sys/arch/vax/include/ansi.h:#ifndef _ANSI_H_

any reason not to turn those all into #ifndef _ANSI_H_ ?