cpplib: Nix -g3.

[Jason Merrill]

>>>>> "Neil" == Neil Booth <neil@daikokuya.demon.co.uk> writes:

> Jason Merrill wrote:-
>> None of the debugging backends actually use this information, so I wouldn't
>> bother if it's at all inconvenient.

> It's already doing it that way.  The # 1 stuff comes out of cppmain.c
> naturally without extra code :-) The only question was should the
> lines be # 0, but if nothing uses it that can wait until something
> does.

Ah.  FWIW, the dwarf2 .debug_macinfo spec requires that command-line macros
have a line number of 0 (and appear before the first DW_MACINFO_start_file
op).

Jason