[Asterisk-Dev] Making functions obsolete

[Olle E. Johansson]

I would like to propose that we officially denounce a couple of functions, not removing them,
but indicating that these are maintained for backwards compatibility and are not recommended
to use. So far I've gathered that these are more or less obsolete:

* IAX version 1 (New: IAX2, according to markster on mailing list)
* prefix, suffix applications (New ${EXTEN} construct)
* DateTime application (New: SayUnixTime)

I'm not sure that all agree, so let's discuss this and if we agree upon something,
change README's, show application texts to indicate this. It'll make life easier for
newbies.

I can update the Wiki and Leif will make sure this is indicated in the new
handbook.

/O