Issue #1167218 by droplet, kathyh: Fixed DatabaseStatementInterface::fetch* - document what empty return value is.

Issue #1291458 by arithmetric: Fixed Database::getConnection mentions short-lived fixed bug and shouldn't.

Issue #561422 follow-up by Damien Tournoud, lyricnz, chx: Fixed SQLite support for faster db prefixes.

Issue #561422 by sun, dalin, lyricnz, catch, Gerhard Killesreiter: Replace strtr() with str_replace() for db prefixing for increased performance.

#977460 by dmitrig01, bfroehle, Josh The Geek: Fixed Cannot serialize or unserialize PDO instances error

- Patch #878198 by pwolanin, Damien Tournoud: add back a method to the DB driver interface that reports the server version.

- Patch #878198 by pwolanin: add back a method to the DB driver interface that reports the server version.

- Patch #195416 by Damien Tournoud, David Strauss: table prefixes should be per database connection.

- Patch #767690 by Crell: @file declarations in database system do not indicate what belongs in the file.

- Patch #742042 by kkaefer:DBTNG: ->fetchAllAssoc() doesn't respect fetch mode set during ->execute().

#299308 follow-up by David_Rothstein: Fixed Installing Drupal by visiting index.php (rather than install.php) leads to a fatal error when PDO is not enabled.

#688294 by Berdir, andypost, Crell, catch: Fixed Switch from db_is_active() to proper exception catching.