Add a check to the PDOAdapter to make sure a statement is returned instead of false

Example problematic code:

https://github.com/cakephp/phinx/blob/master/src/Phinx/Db/Adapter/PdoAdapter.php#L186

I had a SQL operation that was failing because the sqlite adapter was inserting too many rows and failing. The only error returned was the completely unhelpful "cannot call operation on boolean", because the prepare statement failed and was returning false. The fix.

$stmt = $this->getConnection()->prepare($sql);
if (!$stmt) {
    $pdo = $this->getConnection();
     throw new \Exception($pdo->errorCode() . implode($pdo->errorInfo()));
}

I'd do a pull request if I knew what sort of exceptions were wanted for this.

Start at src/Phinx/Db/Adapter/PdoAdapter.php around line 186 and inspect how PDO prepare failures are handled. Review the project's exception conventions before choosing the appropriate exception and include the PDO error information; done means a failed SQLite operation reports its database error instead of attempting to call an operation on false.