Added HTTP support for SDP files.

Added support for playing SDP files from http links. Previously,
SDP files only worked when started from rtsp links
(rtsp://a.b.c/abc.sdp), but they are just as common in http links.

patch provided by "Oscar Rydhé <oscar.rydhe@sonyericsson.com>"

Change-Id: Ic73af3a9a002009dbe8b04c267a4621bf7fe2f46