added comment to every GF.Text.CPxxxx module about the purpose of the codepage

src/compiler/GF/Text/CP1250.hs

@@ -1,3 +1,17 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      : GF.Text.CP1250
+-- Maintainer  : Krasimir Angelov
+--
+-- cp1250 is a code page used under Microsoft Windows to represent texts 
+-- in Central European and Eastern European languages that use Latin script, 
+-- such as Polish, Czech, Slovak, Hungarian, Slovene, Bosnian, Croatian, 
+-- Serbian (Latin script), Romanian and Albanian. It may also be used with 
+-- the German language; German-language texts encoded with cp1250 and cp1252 
+-- are identical.
+--
+-----------------------------------------------------------------------------
+
 module GF.Text.CP1250 where
 
 import Data.Char

src/compiler/GF/Text/CP1251.hs

@@ -1,3 +1,15 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      : GF.Text.CP1251
+-- Maintainer  : Krasimir Angelov
+--
+-- cp1251 is a popular 8-bit character encoding, designed to cover languages
+-- that use the Cyrillic alphabet such as Russian, Bulgarian, Serbian Cyrillic
+-- and other languages. It is the most widely used for encoding the Bulgarian,
+-- Serbian and Macedonian languages.
+--
+-----------------------------------------------------------------------------
+
 module GF.Text.CP1251 where
 
 import Data.Char

src/compiler/GF/Text/CP1252.hs

@@ -1,3 +1,14 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      : GF.Text.CP1252
+-- Maintainer  : Krasimir Angelov
+--
+-- cp1252 is a character encoding of the Latin alphabet, used by default in 
+-- the legacy components of Microsoft Windows in English and some other 
+-- Western languages.
+--
+-----------------------------------------------------------------------------
+
 module GF.Text.CP1252 where
 
 import Data.Char