Bug#908931: transition: gnat-8, Ada component of gcc-8

[Nicolas Boulenguez <nicolas@debian.org>]

Hello.

There was a bug in gprbuild/2018-2 causing reverse dependencies to
FTBFS on many architectures. The last affected package is
* anet on mipsel (Build-Attempted).

gprbuild/2018-3 fixed them, but broke 386 architectures.
* libgnatcoll on i386 (Build-Attempted).
* libgnatcoll on hurd-i386 (Failed).
* libgnatcoll on kfreebsd-i386 (Build-Attempted).

gprbuild/2018-4 fixed them, but broke
* libgnatcoll-db on ia64 (Build-Attempted).

Please trigger rebuild attempts with gprbuild/2018-5.
As this version has not been built yet on kfreebsd-i386, you may also
want to consider adding a dep-wait.

gb           anet_0.4.1-2 . mipsel
gb    libgnatcoll_18.3    . hurd-i386 i386 kfreebsd-i386
gb libgnatcoll-db_18-4    . ia64

dw    libgnatcoll_18-3    . kfreebsd-i386 . -m 'gprbuild (>= 2018-5)'