The gnat-gcc fails to build with texinfo-5.1. This seems to be an gcc doc issue, as in http://gcc.gnu.org/ml/gcc-patches/2013-02/msg00966.html . A patch should be issued or texinfo-5.1 blocked.
*** Bug 476726 has been marked as a duplicate of this bug. ***
Hm, the patch does not seem to apply directly and digging in referenced files shows that they are different. Will have to do it the hard way..
Ok, the failures are different from those in the referenced gcc post; the files are different too. Rather than hunting all these failures I added <texinfo-5.1 to DEPEND. A better course of action would be to stabilize newer gnatgcc. However, if this becomes a problem (say, >=texinfo-5.1 becomes needed for some core package), this bug can be revisited. An actually working patch would be wellcome at this point :). Closing for now.