[9fans] ureg alignment

[erik quanstrom <quanstro@quanstro.net>]

on 64-bit machines, the unions in the ureg.h can lead to
internal padding.  (power64 avoids this issue because everything
is 64-bit aligned anyway.)  to sidestep the issue, i think
it might make sense to use #defines.  for example, for arm
the conversion would look something like this:

typedef struct Ureg {
	ulong	r0;
	ulong	r1;
	ulong	r2;
	ulong	r3;
	ulong	r4;
	ulong	r5;
	ulong	r6;
	ulong	r7;
	ulong	r8;
	ulong	r9;
	ulong	r10;
	ulong	r11;
	ulong	r12;	/* sb */
	ulong	r13;
#define	sp	r13
	ulong	r14;
#define	link	r14
	ulong	type;	/* of exception */
	ulong	psr;
	ulong	pc;	/* interrupted addr */
} Ureg;

is there any reason not to do this?

- erik