Islam: Is it OK to drink alcohol?

I haven't read the Koran and you don't give the context of the first quotation, but as it reads, it could mean that the 'portent' is the apparent dichotomy between the fact that the same plants provide both nourishment and alcohol. The 'people who have sense' will realise that the same plant can offer both good and bad things. There is nothing in the quote you provide to suggest that the strong drink is permitted.