gen_Eq_binds: when comparing constructor tags, emit just

   a == b = case con2tag_Foo# a of
              a# -> case con2tag_Foo# b of b# -> a# PrelGHC.==# b#

and not

   a == b = case con2tag_Foo# a of
              a# -> case con2tag_Foo# b of
                      b# -> if a# PrelGHC.==# b# then PrelBase.True else PrelBase.False

(Not that this wouldn't get simplified, but still).