Obsolete Solaris 10 support

This is the final announcement of the upcoming obsoletion/removal of
Solaris 10 support from GDB.

It has already been proposed on gdb and gdb-patches

	https://sourceware.org/ml/gdb/2019-10/msg00008.html

and the thread mentioned there.  Unless someone steps up to take over
maintenance and testing within a couple of days, the removal patch will
be applied about a week from now.

	Rainer

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Rainer Orth, Center for Biotechnology, Bielefeld University