Add media/libaah_rtp

RTP library used to broadcast media from one device to a collection
of listeners.  Handles failures/retries/etc.

This is a squashed merge from master-tungsten of the following changes:

commit e1a5101fe627d71739a7c4263bb3a65c7bc44385
Author: Jason Simmons <jsimmons@google.com>
Date:   Fri Aug 12 13:24:21 2011 -0700

    Hold ThreadWrapper in a ref-counting pointer

    Change-Id: Iaf3343182e37bcc0ca99fbaf8f9bbb8c4984072a

commit 89b90d62e164ff3db27c9cba85255fc476d2dd96
Author: Jason Simmons <jsimmons@google.com>
Date:   Wed Aug 10 13:08:25 2011 -0700

    Update the Tungsten TX player to use HTTPBase

    Change-Id: I9f7ecf1b4b496cec1815284dbcdb958a43284169

commit 43be3231034ff8537fdd84422a7954780038671f
Author: John Grossman <johngro@google.com>
Date:   Mon Jun 27 18:59:12 2011 -0700

    Move libaah_rtp over from the vendor directory.

    Also move factor PipeEvent out into utils.

    Change-Id: Id3877c66efe22d771cf3ef4877107e431b828e37

Change-Id: I5fe1ea941c09204d7b33f15f4e2b2ab320dc468b
Signed-off-by: Mike J. Chen <mjchen@google.com>
Signed-off-by: John Grossman <johngro@google.com>
Signed-off-by: Jason Simmons <jsimmons@google.com>