[EGL] Initialise resolution to current window size
[omx] Skip the resize when not needed when decoding jpegs

The decode to texture path almost always uses cached jpegs that are the correct size, so the resize is rarely needed.
The re-enc path usually needs resizing, but may not where the source is small.

Skipping the resize stage saves a little time and memory on GPU and also saves some setup time.
[omxplayer] Skip picture attachments in music files they cause audio to hang
[omxplayer] Use media for determing audio delay and cache time

I've also added caching to the call to OMXMediaTime as the GPU round trip is expensive when called too frequently
- before doing the real airplay service zeroconf announcement announce the same thing with different friendlyname - odd try to fix ios7 clients