Suppress spurious "name used only once" warnings

This suggested patch suppresses the

    Name "Bio::EnsEMBL::Slice::config" used only once: possible typo
    Name "Bio::EnsEMBL::DBSQL::StatementHandle::cluck" used only once: possible typo

warnings seen in people's IDEs (see ensembl-dev "VEP script Warnings" from 12 December 2013), and also marks the remaining non-executable scripts as executable.

Now that there are no warnings from variant_effect_predictor.pl (at least in Perl 5.12.3), you might want to add `use warnings;` at the top.