New dump infrastructure

[Sharad Singhai]

> You still have the issue that // regular stuff may appear to possibly
> clobber any_dump_enabled_p and thus repeated any_dump_enabled_p
> checks are not optimized by the compiler (we don't have predicated
> value-numbering (yet)).

> So I prefer the guard.  I suppose after this discussion I prefer
> a any_dump_enabled_p () guard instead of one with (repeated) flags.

I have updated 'dump_enabled_p ()' a little bit in
http://gcc.gnu.org/ml/gcc-patches/2012-10/msg01690.html to avoid
checking of flags. If this looks better, I can update the guard
conditions in vectorization passes from 'if (dump_kind_p (...))' to
'if (dump_enabled_p ())'.

Thanks,
Sharad