[patch] Use tcl8.3 friendly regsub command in gas-defs.exp

[Nick Clifton]

Hi John,

> The enclosed patch fixes PR binutils/5322.  Tested on hppa-unknown-linux-gnu
> with trunk.

Approved and applied.  (I applied the patch locally to check it, so it was just 
as easy for me to check it in afterwards).  I added a comment to the 
gas-defs.exp referencing PR 5322 in case anyone wonders why the tcl is now 
written that way.

Cheers
   Nick