DBAL-112, DBAL-113 - Implement AbstractPlatform::getAlterSequenceSQL() and fix comparator code for sequences

DDC-887 - Fix problem with MySQL renaming of foreign keys columns. The FK has to be dropped, then column renamed, then readded

Fix bug in DropSchemaSQLCollector dropping tables before sequences which can cause constraint errors

DBAL-15 - Add methods for SQL function conversion of types between PHP and database. Implementation inside ORM would now be necessary.

[DBAL-56] Add portability wrapping layer porting MDB2 functionality to fix case, rtrim strings and convert empty strings to null.

[DBAL-78] Add support for native sql list support in positional queries through the introduction of two new constants:

* Doctrine\DBAL\Connection::PARAM_STR_ARRAY
* Doctrine\DBAL\Connection::PARAM_INT_ARRAY

Replacement of arrays only works in conjunction with the Doctrine\DBAL\Connection::executeQuery() and executeUpdate() methods.
You need to pass the param constants into the third parameter called $types.

[DBAL-45] Add reserved keywords feature through platforms and as a validator for any Schema instance with subelements. Add Command to check for reserved keywords in current database.

DBAL-88 - Change index retrieval of MySQL to use information_schema.statistics which avoids errors when using reserved words for table names (for example in database driver).

DBAL-84 - Fix VARCHARs being silently set to 255 chars when larger than Maxlength. Now they are converted to Text/CLOB fields automatically. Refactored the VARCHAR code considerably.