Need for most-used strings contants in SIP

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In LTE context, it would be nice not to have to redefine the following 
constants and that Doubango provides them with #define directives:

- Strings for Event and Allow-Events headers: presence, reg, presence.winfo, 
etc.
- Strings for MIME type: application/reginfo+xml, application/watcherinfo+xml, 
etc.

Maybe, it could be merged with some constants found in XCAP.

Original issue reported on code.google.com by laurent.etiemble@gmail.com on 18 Aug 2010 at 2:36