public: make some constants usable for assembler

public: make some constants usable for assembler

Some constants defined in xen/include/public/xen.h are not usable in
assembler sources as they are either defined with "U" or "UL" suffixes
or they are inside #ifndef __ASSEMBLY__ areas.

Change this as grub2 could make use of those definitions.

This requires to move the definition of mk_unsigned_long() up. While
we are touching this macro, rename it in order to avoid namespace
pollution. This in turn requires adaption of some arch-x86 specific
headers.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Jan Beulich <jbeulich@suse.com>