[RFA] New register definition interface

[Andrew Cagney]

BTW,

In reading the coding standard I would interpret ``try to avoid'' as
``don't do this in new code''. For instance where the standard
indicates:

	Try to avoid assignments inside if-conditions. For example, don't write
this: 

	if ((foo = (char *) malloc (sizeof *foo)) == 0)
	  fatal ("virtual memory exhausted");

I'd interpret it as don't do this in new code.  Even though there are
many examples in existing code.

	Andrew