options: tiny simplification in dealing with incompatible versions

options: tiny simplification in dealing with incompatible versions

* lib/Automake/Options.pm (_process_option_list): Here, when an
incompatible version number option is detected, there's no need
to call error() with the "uniq_scope => US_GLOBAL" switch.
In fact, if the same incompatible version number is specified in
AUTOMAKE_OPTIONS in both (say) 'Makefile.am' and 'sub/Makefile.am',
we want each such erroneous usage reported separately, rather than
just the first time it is encountered (as we'd expect to happen
when "uniq_scope => US_GLOBAL" is used).
Ideally, this change should have been folded into the similar
commit 'v1.13.1d-129-gf7ef16f', but we noticed that too late.
Oh well.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>