tools/libs: ROUNDUP() related adjustments

tools/libs: ROUNDUP() related adjustments

For one xc_private.h needlessly repeats xen-tools/libs.h's definition.

And then there are two suspicious uses (resulting from the inconsistency
with the respective 2nd parameter of DIV_ROUNDUP()): While the one in
tools/console/daemon/io.c - as per the code comment - intentionally uses
8 as the second argument (meaning to align to a multiple of 256), the
one in alloc_magic_pages_hvm() pretty certainly does not: There the goal
is to align to a uint64_t boundary, for the following module struct to
end up aligned.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: Ian Jackson <iwj@xenproject.org>