Fixed dir typo in INSTALL.osx

darcs-hash:20081126085518-58103-d2e688fc8770757d937560edb17d0574a0f3fc59
For for being able to query SDP on Invitation object after it is DISCONNECTED

darcs-hash:20081126095300-58103-3185bd4cb3441b908740f3e64c584f8fc9207fdf