Add "extraneous parentheses" compiler warning for anonymous methods

[Kurper]

things like
def init()
generate compiler warnings, since
def init
works just as well. but
listen .click, do()
does not produce a warning, even though
listen .click, do
works. Alternately, if you think that the first form is superior (since it's more obvious what's going on), perhaps the second form should be disallowed.

[Chuck]

Fixed in changeset:1997 and changeset:1998
Fixed for lambdas as well.