pg_basebackup streaming: adjust version check msg

Commit d298b50a3b469c088bb40a4d36d38111b4cd574d by Heikki Linnakangas
requested that the version check message be updated at next release, suggesting
that the appropriate text would be “9.3 or later”. The logic used for the check
indicates that the correct text for 9.4 is “9.3 or 9.4”, since the logic would
cause this to fail for later releases.
More rewording of pg_stat_statements for 9.4 release notes

Report by Amit Langote