Fixup notes about updating the version number.

The version number is kept in VERSION, however since README is no-longer
dynamically generated we must also update the version number there.
This change adds a note to this effect in VERSION.

VERSION:
    As above.
Update the copyright year

bindist/bindist.README:
compiler/handle_options.m:
doc/faq.texi:
doc/library.texi:
doc/reference_manual.texi:
doc/transition_guide.texi:
doc/user_guide.texi:
profiler/mercury_profile.m:
trace/mercury_trace_internal.c:
    As above.