EUROCONVERT: add reference to the European Commission's conversion rates; new rates may appear

Change Summary from Converts a number from one to another Euro currency. to Converts a Number, representing a value in one European currency, to an equivalent value in another European currency, according to the fixed conversion rates defined by the Council of the European Union. Change Semantics from The function must be able to convert between the Euro ("EUR") and various older European countries. In this case, it must use the rates of exchange as set by the European Commission, as follows: to The function shall use the rates of exchange as set by the European Commission, as follows: Add to Semantics: As new member countries adopt the Euro, new conversion rates will become active and implementations may add them using the respective ISO 4217 codes and fixed rates as defined by the European Council, on the basis of a European Commission proposal. The European Commission's Euro entry page is http://ec.europa.eu/euro/ The conversion rates and triangulation rules are available at http://ec.europa.eu/economy_finance/the_euro/joining_euro9405_en.htm with links to the European Council Regulation legal documents at the http://eur-lex.europa.eu/ European Union law database server.