Fix many to many polymorphic pivot updates

`$morphType ` set by `setMorphType` is being included in queries from x->pivot->save() and the like. As the object is being added as a public data member on an object with an empty original, it is treated as an attribute and added as a column to the queries. As this column doesn't exist, the query will be erroneous.

https://github.com/laravel/framework/issues/3693
Eloquent Pivot - Make sure raw attributes setting also set's original data

Fixes bug that calls db update from pivot models that haven't even changed
Merge pull request #4288 from skovacs1/4.1

[Bug] Fix many to many polymorphic pivot updates
Add note.
Merge branch '4.1' into 4.2
Add updateOrCreate() function
Merge pull request #4602 from lucasmichot/4.2-model-updateorcreate

[4.2] Add updateOrCreate() function
Spacing.
Update change log.
Merge pull request #4603 from jmshelby/pivot-sync-original

Eloquent Pivot - Make sure original attribute values are being set on call to setRawAttributes
Updated connection interface
Removed extra line
Revert abstract class change.
Restore the ability to easily override the compilers
Table prefix was added twice

If a table prefix was set in the database config, this code caused the prefix to be added twice: once here and once in the call to the database engine inside `DatabaseSessionHandler`. refs #4580 on the correct branch.
Merge pull request #4609 from kohenkatz/4.2

Table prefix was added twice
Merge pull request #4605 from GrahamCampbell/4.2-views

[4.2] Restore The Ability To Easily Override The Compilers
Merge pull request #4604 from GrahamCampbell/4.2-db

Updated Connection Interface