Obsoleting Solaris 10 support

[Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>]

Yesterday I've announced the obsoletion of Solaris 10 support in GCC 9

	https://gcc.gnu.org/ml/gcc/2018-10/msg00139.html

I believe the same reasons cited there hold for GDB as well.  Besides,
we had some build failures recently that only occured on Solaris 10,
creating work to support a rapidly dwindling or even vanished user base.
Therefore, I wonder how best to handle this in GDB.

While GCC has roughly one release a year and GCC 9, the last relase to
support Solaris 10 with --enable-obsolete, will appear sometime next
spring, GDB has a release cycle of about 6 months.  Should we obsolete
Solaris 10 for GDB 8.3 now, getting a bit ahead of GCC, or rather wait
for GDB 8.4 instead?  My gut feeling is that it would be better to wait
for 8.4: more often than not GCC adds support for new DWARF versions or
other extensions, and it would be good to have a GDB that supports
what's in the GCC 9 release.

Thanks.
        Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University