fix length check of node, domain and resource identifier

• Acceptance Test - Add?:

  No

RFC3920 does define:

Each allowable portion of a JID (node identifier, domain identifier, and resource identifier) MUST NOT be more than 1023 bytes in length, resulting in a maximum total size (including the '@' and '/' separators) of 3071 bytes.

I've seen this problem just in org.xmpp.packet.JID, line 368, "if (domain.length()*2 > 1023) {" but it may occur also somewhere else.
The right way to check the length in this case is domain.getBytes("UTF-8").length to match the requirement "1023 bytes in length".

Short sample code:

String y = "\u0001\uD11E";

// 2
System.out.println(y.length());

// 4
System.out.println(y.getBytes("UTF-8").length);         

// "\u20AC"
String z = "€";                                                                     

// 1
System.out.println(z.length());                                        

// 3
System.out.println(z.getBytes("UTF-8").length);

reference: http://de.wikipedia.org/wiki/UTF-8 - "Beispiele für UTF-8 Kodierungen"