Fix escaping of column name for specific alter table case

Unit tests currently only cover SQLite, MySQL and PostgreSQL.

Tests for other platforms have been marked as incomplete.

improved sqlserver 'doModifyLimitQuery' select-from pattern

with assertEquals

Allow to connect without a dbname param

The PDO connection allow the instantiation of the connection even if the dbname
parameter isn't present. This change is there to make sure both behave the same way.

When changing the length of a field, the column name needs to be escaped
properly.

Fix pg boolean conversion

PG specific attribute PDO::PGSQL_ATTR_DISABLE_NATIVE_PREPARED_STATEMENT is now only set when it is still supported

reverted @deeky666 suggestion. Since it failed on testBooleanNullConvertsToPHPValue test. 
with message Failed asserting that true is null.
Since I moved this code from BoolenType::convertToPHPValue in the first place, I presume the code there correct.

Updated test for uppercased values