Clean up the macros to avoid using casts.

Suggested by: bde and jhb
Fix accounting for hw.realmem on the i386 and amd64 platforms.

sys/i386/i386/machdep.c:
sys/amd64/amd64/machdep.c:
	The value reported by FreeBSD as "real memory" when booting
	doesn't match what is later reported by sysctl as hw.realmem.
	This is due to the fact that the value printed during the
	boot process is fetched from smbios data (when possible),
	and accounts for holes in physical memory. On the other
	hand, the value of hw.realmem is unconditionally set to be
	one larger than the highest page of the physical address
	space.

	Fix this by setting hw.realmem to the same value printed
	during boot, this makes hw.realmem honour it's name and
	account properly for physical memory present in the system.

Submitted by:	Roger Pau Monné
Reviewed by:	gibbs
Remove an incorrectly copied and pasted clause from these license
statements.

Approved by:	Yohanes Nugroho <yohanes@gmail.com>
MFC after:	1 week