HHVM compatibility: implement declared interfaces

HHVM does not allow declaration of interface implementation without
real implementation of methods which parameters differs from parent
class.
Fixed compatibility with PHP PDO
Fixed equal sign
fix binding LOB values in mysqli driver prepared statement
only store result in mysqli driver prepared statement if a result is definitely available
phpdoc in Table::addForeignKey() update
another cases also updated
Added some documentation for the drizzle driver.
Moved drizzle content under pdo_mysql sections.
Added some clarification to drizzle doc.
Merge pull request #443 from kimhemsoe/drizzle_docs

Added some documentation for the drizzle driver.
fix typo
Merge pull request #373 from javer/hhvm-pdo-implement-interfaces

HHVM compatibility: implement declared interfaces
Add hhvm to build matrix
Merge pull request #433 from deeky666/fix-mysqli-driver-bind-lob-values

Fix binding LOB values in mysqli driver prepared statement
Merge pull request #436 from velosipedist/hotfix/PhpDoc

phpdoc in Table::addForeignKey() update
Added some mysqli documentation.
Merge pull request #445 from kimhemsoe/mysqli_docs

Added some mysqli documentation.