x86: automatical unification of i8259.c

Make conversion of i8259 very mechanical -- i8259 was generated by
 diff -D, with too different parts left in i8259_32 and
i8259_64.c. Only "by hand" changes were removal of #ifdef from middle
of the comment (prevented compilation) and removal of one static to
allow splitting into files.

Of course, it will need some cleanups now, and those will follow.

Signed-of-by: Pavel Machek <pavel@suse.cz>