RFC: More stuff in struct bfd_link_info

[Hans-Peter Nilsson]

There's a some target-specific cruft in struct bfd_link_info
(for example "int mpc860c0" and "boolean pei386_auto_import")
that could go away (or at least not accumulate) if there was
just a target-specific PTR member, say "PTR target_data".

Also, I'd like to move "boolean relax" from ld.h:args_type to
struct bfd_link_info, so bfd functions can see whether
relaxation should be done, and perhaps also set it (only) when
necessary; for example if some presumably costly relaxation only
needs to be done if certain relocs are present.

Thoughts?

brgds, H-P