[Patch, Fortran] PR 40941: gfc_typespec: put derived, cl and interface into union

[Janus Weil]

>> The patch is regtested on x86_64-unknown-linux-gnu. I will write a
>> ChangeLog soon (although I'm not looking forward to it).
>
> I propose that with the exception of the above non-mechanical changes,
> you indicate the files that have been modified and say that all
> occurrences of ts.cl and ts.derived have been modified to accommodate
> the union, which should be described in the gfortran.h entry.
>
> OK for trunk

Committed as r150725.

Side note: When regtesting today I got some additional failures which
I did not see last week (though I have no idea why). I made another
small change in trans-io.c to fix them, and ran the testsuite again
before committing (everything is clean now).

Cheers,
Janus