gnunet-config and build informations (bug #5708)

[Alessio Vanni]

Hello,

I made an attempt at implementing what was discussed in bug #5708 [0],
that is, additional flags for `gnunet-config' to print various
informations similar to what other `*-config' tools do
(e.g. `nss-config'.)

After sending this mail I'm going to push a branch called
'dev/vanni/build-info'; it's a separate branch because even though the
changes are very simple (even including the documentation), I'd like to
get some feedback first, especially if more flags are requested.

The following is a bit off-topic, but since it's something that might
leverage the new gnunet-config flags, I'm going to ask here regardless.

Would it be possible to provide with the core GNUnet installation an
Autoconf macro to detect GNUnet properly?  I'm using Autoconf to manage
the GNUnet-based applications I'm writing, but detecting GNUnet is a bit
of a mess.

Of course with the new gnunet-config I can just rely on it, but if I had
a macro provided by GNUnet itself, much like other programs like for
example Guile Scheme do [1], it'd be better.

This is especially true as getting a third-party GNUnet-based
application to compile has surprising caveats: a very noticeable one is
that, apparently, the `netinet/in.h' header is required when neither
`gnunet_config.h' nor `platform.h' are `#include'd (which is what
happens with third-party applications, at least those built using
Autoconf.)

This is something that can be noticed only when the program is actually
compiled, but with a GNUnet-specific macro the check for the necessary
headers (and all that it entails) can be done implicitly by the macro
itself.

I've made an attempt locally which first uses pkg-config and then falls
back to the new gnunet-config, but before pushing it to the remote
repository I'd like, once again, to hear some feedback on the matter, be
it to pay attention to certain configurations or even be just a matter
of following certain conventions.

Thank you,
A.V.

---

[0] https://bugs.gnunet.org/view.php?id=5708
[1] 
http://git.savannah.gnu.org/gitweb/?p=guile.git;a=blob;f=meta/guile.m4;h=48642f027f7b002d40658511fe3bb831e83ebdfc;hb=HEAD