WL#4579: Latin9 (iso-8859-15) character set

Add Latin9 (iso-8859-15) character set.

This task is a part of Sun Globalization Requirements.

Character set name
==================
MySQL character set name will be "latin9".

Collations
==========

* latin9_bin
* latin9_danish_ci - also good for Norwegian.
* latin9_general_ci - for English, French, German Dictionary, Italian, Dutch,
Portuguese, Malay. Will provide the same sorting order as latin1_general_ci.
* latin9_general_cs
* latin9_german1_ci
* latin9_german2_ci - German Phonebook.
* latin9_spanish_ci - Modern Spanish.
* latin9_swedish_ci - also good for Finnish

The default collation will be latin9_swedish_ci

Collations will have the same sorting order with the corresponding
latin1 collations.

What the reviewer looks for
===========================

The code reviewer will look for: 
- Every operation that is applicable to latin1, for example converting
  + using in CHARACTER SET clause + using in introducer + finding in
  information_schema.character_sets, will be applicable to latin9.
- The characters and conversions are as in these "authoritative" charts:
  ftp://ftp.unicode.org/Public/MAPPINGS/ISO8859/8859-15.TXT
  http://en.wikipedia.org/wiki/ISO/IEC_8859-15

Misc
====
Implementor will uncomment the currently hidden code in sql-common/client.c

#ifdef UNCOMMENT_THIS_WHEN_WL_4579_IS_DONE
  {"iso885915",      "latin9",   my_cs_exact},
  {"ISO_8859-15",    "latin9",   my_cs_exact},
  {"ISO8859-15",     "latin9",   my_cs_exact},
  {"ISO-8859-15",    "latin9",   my_cs_exact},
#endif


References:
===========
BUG#18576 - Latin1 character set is obsolete, should use euro-compatible latin9
as default
BUG#37738 - Latin9 for MySQL