Add %mrp pseudo-register to hppa assembler

[Nick Clifton]

Hi Matthew,

> 2001-06-19  Matthew Wilcox  <willy@ldl.fc.hp.com>
> 
> 	* config/tc-hppa.c: Add %mrp (millicode return pointer) alias
> 	for %r2 or %r31, depending on 32 or 64 bit architecture.

Approved and applied.

Thanks!

        Nick