Lexer generates incorrect token sequence

[erikd]

For the function:

trick2 xs = [ (x, y)
		| x <- xs
		, let y = x `mod` 3 ]

the lexer generates a token sequence (ignoring other tokens) of "[ { ] }" where the brackets don't match up properly. Changing the code to:

trick2 xs = [ (x, y)
		| x <- xs
		, let y = x `mod` 3
		]

generates the correct sqeuence of "[ { } ]".

[erikd]

This bug depends on and can't really be worked on until #171 is fixed.

[erikd]

This is a simpler version of bug #161.