Updating charset doc files.

Thanks to Paul for preparing the up-to-date files
reflecting 4.1 changes.

sql/share/charsets/README

-This directory holds configuration files which allow MySQL to work with
+This directory holds configuration files that enable MySQL to work with
 different character sets.  It contains:
 
-*.conf
-    Each conf file contains four tables which describe character types,
+charset_name.xml
+    Each charset_name.xml file contains information for a simple character
+    set.  The information in the file describes character types,
     lower- and upper-case equivalencies and sorting orders for the
     character values in the set.
 
-Index
-    The Index file lists all of the available charset configurations.
+Index.xml
+    The Index.xml file lists all of the available charset configurations,
+    including collations.
 
-    Each charset is paired with a number.  The number is stored
-    IN THE DATABASE TABLE FILES and must not be changed.  Always
-    add new character sets to the end of the list, so that the
-    numbers of the other character sets will not be changed.
+    Each collation must have a unique number.  The number is stored
+    IN THE DATABASE TABLE FILES and must not be changed.
+
+    The max-id attribute of the <charsets> element must be set to
+    the largest collation number.
 
 Compiled in or configuration file?
     When should a character set be compiled in to MySQL's string library
-    (libmystrings), and when should it be placed in a configuration
-    file?
+    (libmystrings), and when should it be placed in a charset_name.xml
+    configuration file?
 
     If the character set requires the strcoll functions or is a
     multi-byte character set, it MUST be compiled in to the string
     library.  If it does not require these functions, it should be
-    placed in a configuration file.
+    placed in a charset_name.xml configuration file.
 
     If the character set uses any one of the strcoll functions, it
     must define all of them.  Likewise, if the set uses one of the
@@ -30,11 +33,7 @@ Compiled in or configuration file?
     more information on how to add a complex character set to MySQL.
 
 Syntax of configuration files
-    The syntax is very simple.  Comments start with a '#' character and
-    proceed to the end of the line.  Words are separated by arbitrary
-    amounts of whitespace.
-
-    For the character set configuration files, every word must be a
-    number in hexadecimal format.  The ctype array takes up the first
-    257 words; the to_lower, to_upper and sort_order arrays take up 256
-    words each after that.
+    The syntax is very simple.  Words in <map> array elements are
+    separated by arbitrary amounts of whitespace. Each word must be a
+    number in hexadecimal format.  The ctype array has 257 words; the
+    other arrays (lower, upper, etc.) take up 256 words each after that.