Nikkei hits 8-1/2 mth high on weak yen, nears level before Lehman crash

* Nikkei highest since Dec, nears pre financial crisis level * Yen drops to six-year low vs dollar after vote went against Scottish independence * Long-term investors cautious against steep rise - analysts By Ayai Tomisawa TOKYO, Sept 19 (Reuters) - Japanese stocks extended gains to an 8-1/2 month high on Friday after the yen dropped to a six-year low, underpinned by the Federal Reserve's policy outlook, and after the first result in the Scottish independence vote went to the u