Structure, current version

An extra parameter i has been introduced. 
data EI i e p ds t c    = ...	-- Expressions
data DI i e p ds t c tp = ...	-- Declarations
data PI i   p           = ...	-- Patterns
data TI i        t      = ...	-- Types

data HsIdentI i =  HsVar i | HsCon i	-- Identifiers
Implementations: EI, DI, PI, TI, HsIdentI.

Backwards compatiblity

type E = EI HsName
mapE = mapEI id

type HsIdent = HsIdentI HsName
...
Implementations: mapEI in module HsExpMaps, ...