Bad RPID <person> id attribute generation (thanks Filipe Figueiredo for the report)

[bennylp]

Quoting Filipe's email in ​http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/2009-October/009080.html:

The creation of the id attribute for the XML element "person" is not valid. The string being generated needs to start with a letter or an underscore, as specified on the XML Schema for this attribute.

The XML schema for this attribute can be found on ​http://www.apps.ietf.org/rfc/rfc4479.html, page 26:

<xs:attribute name="id" type="xs:ID" use="required"/>

According with the definition of the xs:ID (​http://www.w3.org/TR/2000/CR-xmlschema-2-20001024/#ID):

"The lexical space of ID is the set of all strings that match the NCName production in[Namespaces in XML]."

The specification of the NCName is the following:

[4] NCName ::= NCNameStartChar NCNameChar*
[5] NCNameChar ::= NameChar - ':'
[6] NCNameStartChar ::= Letter | '_'

[bennylp]

In r2935:

• make sure the id starts with letter