[Agda] pattern matching syntax in records

[Chris Casinghino]

> No. Declarations (including definitions by pattern matching and where
> clauses) are not allowed inside expressions (this includes record
> values, lambda abstractions and let expressions).

Thanks for clarifying.  I suppose I should have looked up the grammar
first!  I just assumed let and where clauses were in the same
syntactic category.

I am curious to hear why this distinction is important, and if it
could be weakened in this case.

--Chris