amd64: -m32 support for machine/vmparam.h

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

Reviewed by:	jhb, imp

include/i386/Makefile

@@ -9,7 +9,8 @@ INCS=	\
 	pmap.h \
 	proc.h \
 	profile.h \
-	segments.h
+	segments.h \
+	vmparam.h
 INCSDIR=	${INCLUDEDIR}/i386
 
 .include <bsd.prog.mk>

sys/amd64/include/vmparam.h

@@ -43,6 +43,10 @@
  * $FreeBSD$
  */
 
+#ifdef __i386__
+#include <i386/vmparam.h>
+#else /* !__i386__ */
+
 #ifndef _MACHINE_VMPARAM_H_
 #define	_MACHINE_VMPARAM_H_ 1
 
@@ -302,3 +306,5 @@
 #define MINIDUMP_PAGE_TRACKING	1
 
 #endif /* _MACHINE_VMPARAM_H_ */
+
+#endif /* __i386__ */