Load plugins when ProjectData is different (patch) (part 2)

[Alessio Vanni]

Hello,

a few months ago, I had submitted a patch[0] to solve a problem
involving loading plugins and third-party applications, which was not
applied for a number of reasons.

I hoped to submit another patch sooner than now, but unfortunately I
ended up not being able to. Anyway, the attached patch should be more in
line with the solution suggested in the responses of [0].

It also contains a small change to the `datacache.c' file, as it's the
only part of the codebase using `GNUNET_PLUGIN_load' (as far as I
understood) which is exposed to third-party applications. To avoid the
same issues which the new function introduced by the patch tries to
solve, I added a few lines which are essentially the "expansion" of the
function, as appropriate for the surrounding code.

Unfortunately, I couldn't implement one of the proposed changes, that
is, making the context thread-local.  I know that there is a macro which
simply expands to the built-in `__thread' (where appliable) and that
there are a few uses in the code, but I'm still not too sure how it
works within GNUnet, so I prefer to submit this patch while I try to
understand the rest.

Thanks,
A.V.

[0] https://lists.gnu.org/archive/html/gnunet-developers/2020-12/msg00008.html

0001-Implement-function-to-load-plugins-within-a-specific.patch
Description: patch for gnunet