RFC: .sleb128 and bignums

[Nick Clifton]

Hi Richard,

> gas/
> 	* read.c (convert_to_bignum): New function, split out from...
> 	(emit_expr): ...here.  Handle the case where X_add_number is
> 	positive and the input value is negative.
> 	(output_big_sleb128): Fix setting of continuation bit.  Check whether
> 	the final byte needs to be sign-extended.  Fix size-shrinking loop.
> 	(emit_leb128_expr): When generating a signed leb128, see whether the
> 	sign of an O_constant's X_add_number matches the sign of the input
> 	value.  Use a bignum if not.
> 
> gas/testsuite/
> 	* gas/all/sleb128.[sd]: New test.
> 	* gas/all/quad.[sd]: New test.
> 	* gas/all/gas.exp: Run them.

Approved - please apply.

Cheers
   Nick