amd64: -m32 support for machine/asm(macros).h

Install the i386 versions under /usr/include/i386 on amd64 and include
when targeting i386.

Reviewed by:	jhb, imp

include/i386/Makefile

@@ -2,6 +2,8 @@
 
 .PATH: ${SRCTOP}/sys/i386/include
 INCS=	\
+	asm.h \
+	asmacros.h \
 	cpufunc.h \
 	profile.h
 INCSDIR=	${INCLUDEDIR}/i386

sys/amd64/include/asm.h

@@ -35,6 +35,10 @@
  * $FreeBSD$
  */
 
+#ifdef __i386__
+#include <i386/asm.h>
+#else /* !__i386__ */
+
 #ifndef _MACHINE_ASM_H_
 #define	_MACHINE_ASM_H_
 
@@ -110,3 +114,5 @@
 #endif /* !STRIP_FBSDID */
 
 #endif /* !_MACHINE_ASM_H_ */
+
+#endif /* __i386__ */

sys/amd64/include/asmacros.h

@@ -39,6 +39,10 @@
  * $FreeBSD$
  */
 
+#if defined(__i386__)
+#include <i386/asmacros.h>
+#else /* !__i386__ */
+
 #ifndef _MACHINE_ASMACROS_H_
 #define _MACHINE_ASMACROS_H_
 
@@ -264,3 +268,5 @@ X\vec_name:
 #endif /* __STDC__ */
 
 #endif /* !_MACHINE_ASMACROS_H_ */
+
+#endif /* __i386__ */