Screen/GStreamer: Make movie writing work better with GStreamer SDK.

SDK version 2013.6 adds support for x264enc, so H264+AAC+QT encoding
is now possible. However, the faac encoder is missing. Instead the
ffenc_aac encoder is available. Make the codec setup code auto-detect
this: If faac is present, use it for AAC encoding. Otherwise fall back
to ffenc_aac, which might be slightly lower quality, according to the
upstream documentation.

Also make sure no audio-codec is created or setup if writing of video
only movies is requested. This to avoid irrelevant warning clutter.

Also add notice that GStreamer-1.0 is not yet supported by PTB if
GStreamer-0.10 init fails. This because Homebrew now ships v1.0 by
default, so users might be confused if Homebrew gstreamer stops
working.

-> Makes movie writing work out of the box on OSX with 2013.6 SDK.
-> Screen for 64-Bit Octave/Matlab on OSX rebuilt against 2013.6 SDK.
-> ImagingStereoDemo.m - Movie writing setup code simplified + additional
   info about setting codec parameters.

-> If this Screen() files are used against a Homebrew GStreamer, then
   glib must be up to date, otherwise crash will occur.

Known issues with the 2013.6 SDK:

1. Looped playback with some movies that have sound doesn't work reliably:
Hangs, Timeouts, loss of sound on 2nd/3rd/... iteration or wrong playback
speed on all but the 1st iteration.

2. LoadMovieIntoTexturesDemo approach doesn't work with some movies that
have sound -> Hangs.

3. Videocapture still doesn't work! (wtf. QA?!?)
DrawText text renderer plugin: Fix dormant bug and make robust against weird fonts.

* Fix bug where TranslucentTexture:: invertPixmap routine used bitmap.pitch where
  it should have used bitmap.width. Bug never seen in reality, as bitmap.pitch == bitmap.width
  in apparently all real-world setups. But anyway, better safe than sorry.

* Add safety check to monochrome renderer to reject bitmaps other than 1bpp, as
  that would crash. Never seen in the wild, but better safe than sorry.

* Fix crash in anti-aliased renderer if it was fed with a 1 bpp monochrome bitmap
  instead of the expected 8 bpp bitmap. This would crash hard and did so on an
  ancient Gentoo Linux system of a user (forum msg #15827 et al.).

  If we detect such a non 8 bpp input bitmap, we try to convert it on the fly
  into a suitable 8 bpp bitmap via the FT_Bitmap_Convert() function.

-> OGLFT.cpp modified.
-> Drawtext FTGL plugin rebuilt and tested on 32/64 Bit Linux and OSX. User will
   test on the troublesome Gentoo Linux system and report back.
Screen/Linux: Try to prevent loss of window focus for hidden windows.

Try to prevent loss of keyboard input focus for active window if
a hidden onscreen window (windowshieldinglevel == -1) is created.

Incorporate latest GStreamer changes into Screen.

-> Screen for 32/64 Bit Matlab and Octave on Linux rebuilt and tested.