Adding quite a few intrinsics

[François-Xavier Coudert]

> +  add_sym_2 ("xor", 1, 0, BT_UNKNOWN, 0, GFC_STD_F95,
>
> This should be GFC_STD_GNU.

Right.

> In fact, I think BM:s definition is so good that we should adopt it,
> and spell it out in the documentation, so that our users will
> understand the distinction too.

Well, I don't agree with this definition. That would mean that code
that compiled out of the box with g77 will not compile with gfortran
unless you give it the -std=legacy flag, which:

  1. sounds like saying "please dump that big concrete block on me",
and most probably people will be reluctant to do it

  2. will break configury scripts, like the GNU auto* tools

  3. will get an endless crown of people asking on our list why their
code doesn't run :)

FX