Many database driver classes have no class doc blocks

As I understand it, this is rc eligible.

@dropdan Nice work! What is the significance of the different wording for the SQLite classes?

1. +++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Update.php
   @@ -11,6 +11,9 @@
   +/**
   + * Implements the Update query for the PostgreSQL database driver.
   + */
   

2. +++ b/core/lib/Drupal/Core/Database/Driver/sqlite/Merge.php
   @@ -9,4 +9,7 @@
   +/**
   + * SQLite specific implementation of \Drupal\Core\Database\Query\Merge.
   + */
   

For core/lib/Drupal/Core/Database/Driver/sqlite/Upsert.php comment was already set and it is "SQLite specific implementation of" and for core/lib/Drupal/Core/Database/Driver/pgsql/Upsert.php and mysql too, is "Implements the [class] query for the [*]SQL database driver." so the only option was to keep the wording template or to change it for the Upsert class.

Please review my patch

Please ignore last patch , uploading correct patch

Please find updated patch

+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
@@ -21,6 +21,9 @@
+/**
+ * Implements the DatabaseConnetion for the MySQL database driver.
+ */
 class Connection extends DatabaseConnection {

Re #9, this should be "MySQL implementation of DatabaseConnection.", and similarly with the ones following. We want them all on the same pattern.

Please check updated patch

1. +++ b/core/lib/Drupal/Core/Database/Driver/mysql/Delete.php
   @@ -9,4 +9,7 @@
    
   +/**
   + * MySQL implementation of DeleteQuery.
   + */
    class Delete extends QueryDelete { }
   

   Should this be "MySQL implementation of Delete."?

2. +++ b/core/lib/Drupal/Core/Database/Driver/mysql/Insert.php
   @@ -9,6 +9,9 @@
   +/**
   + * MySQL implementation of InsertQuery.
   + */
    class Insert extends QueryInsert {
   

   Should this be "MySQL implementation of Insert."?

3. +++ b/core/lib/Drupal/Core/Database/Driver/mysql/Merge.php
   @@ -9,4 +9,7 @@
    use Drupal\Core\Database\Query\Merge as QueryMerge;
    
   +/**
   + * MySQL implementation of MergeQuery.
   + */
   

   Should this be "MySQL implementation of Merge."?

4. +++ b/core/lib/Drupal/Core/Database/Driver/mysql/Select.php
   @@ -9,4 +9,7 @@
   +/**
   + * MySQL implementation of SelectQuery.
   + */
    class Select extends QuerySelect { }
   

   Should this be "MySQL implementation of Select."?

5. +++ b/core/lib/Drupal/Core/Database/Driver/mysql/Transaction.php
   @@ -9,4 +9,7 @@
    use Drupal\Core\Database\Transaction as DatabaseTransaction;
    
   +/**
   + * MySQL implementation of DatabaseTransaction.
   + */
    class Transaction extends DatabaseTransaction { }
   

   This should be "MySQL implementation of Transaction.".

I think there are more, but each of these comments should refer to the real class name being implemented, not the alias from the use statement.

That is much better.

Umm! You're right! reverting Statement.php.

@jhodgdon what about :

/**
 * SQLite implementation of \Drupal\Core\Database\StatementPrefetch.
 *

Hi Jhodgdon,
Changed "SQLite implementation of DatabaseConnection." to "SQLite implementation of Statement." Is this what you suggested. If not, could you suggest on this.

Adding namespace.

Done.

Committed 7e245c9 and pushed to 8.0.x. Thanks!