[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.

[DBAL-42] Optimized column comment change detection. Ignore from columns with a null comment which indicates not set compared to an empty string which says delete comment.

[DBAL-42] Add support to reverse engineer Comments from MySQL, PostgreSQL and ORacle into Doctrine\DBAL\Schema\Column instances and added comment comparison into Comparator.

DBAL-91 - Fix auto-generation of asset names (foreign keys and indexes) which could lead to exceptions due to auto-quoting of PostgreSQL for example. Now hashing the names with crc32+dechex