The other answers have corrected my original answer by noting that Shakespeare didn't write the possessive with the apostrophe 's. However, the possessive used in Early Modern English was generally pronounced the way it is today, and modern editors have changed Shakespeare's spelling into an 's. There was a difference in pronunciation from modern-day usage, though. If a word ended with an "s" in an unaccented syllable, the possessive was pronounced the same way as the base word, and only an apostrophe was added.
Some examples from Shakespeare:
From _Othello:_
> He'll be as full of quarrel and offence
> As my young mistress' dog.
From _The Merchant of Venice_ :
> But stop my house's ears, I mean my casements.
From _Henry VI, Part II:_
> For underneath an alehouse' paltry sign.
From _Henry V:_
> Let us not hang like roping icicles
> Upon our houses' thatch.