gdbsupport: regenerate Makefile.in

gdbsupport: regenerate Makefile.in

I had cause to regenerate gdbsupport/Makefile.in, and noticed some
unexpected changes in the copyright header dates.

I suspect that this was caused by the end of year date range update
process.

The Makefile.in contains two date ranges.  The first range appears to
be the date range for the version of automake being used, that is the
range runs up to 2017 only, when automake 1.15.1 was released.

The second date range in Makefile.in represents the date range for the
generated file, and so, now runs up to 2022.

Anyway, this is the result of running autoreconf (using automake
1.15.1) in the gdbsupport directory.