[patch] Add discriminator support to gas .loc directive

[Nick Clifton]

Hi Cary,

> Tested on i386. Is this OK for trunk?

Almost, but not quite:

   * Please add a line to gas/NEWS mentioning the new feature and extend 
the description of the .loc directive in gas/doc/as.texinfo.

   * Why do you allow the user to set a value of 0 for the descriminator 
when only values greater than 0 are emitted ?

Cheers
   Nick

PS.  When you submit the binutils/dwarf.c patch please could you also 
extend the gas/testsuite/gas/lns/lns-common-1.s test to cover the new 
sub-command.