Screen/Windows: Switch compile to GStreamer-1.0, fix build failure.

Switch to build against GStreamer-1.4.0.
Fix a small compile failure.
Screen: Fix all compiler warnings when building on Windows.
Screen: Fix delay loading on Windows with GStreamer-1.4

Need to replace all instances of
GST_VALUE_HOLDS_FRACTION/LIST/FRACTION_RANGE by G_VALUE_HOLDS(xxxx,
get_fraction_range_get_type()) etc. and GST_TYPE_FRACTION by
gst_fraction_get_type()

Why? Using the macros will inline some stuff from
libgstreamer-1.0-0.dll which will prevent delay-loading of said DLL and
thereby prevent delay loading of GStreamer as a whole. Using the
gst_xxxx_get_type() functions adds just enough indirection to prevent
the delay-load problems.

-> Delay loading works. Screen() works on a system without
GStreamer-1.4.0 or later installed, as long as one doesn’t use
GStreamer based functionality. If the movie playback/writing or Video
capture/recording functions are used, Screen() will abort with a
helpful message, directing the user to install GStreamer-1.4.0 or later.

-> First delay-loadable Screen.mexw64 for 64-Bit Matlab on Windows
included. Not yet actually tested with new GStreamer backend, but it
compiles, loads, works with basic functions.
VideoRecordingDemo: Switch to directsoundsrc on Windows.

dshowaudiosrc doesn’t (yet? ever?) exist in GStreamer-1.4, but
directsoundsrc does exist.
Adapt VideoDVCamCaptureDemo to GStreamer-1.x
PsychStartup: Update for GStreamer-1.4+ on 64-Bit Windows.

Make it detect the new env variable with the path to the GStreamer-1.4
runtime and do proper setup, so it works with PTB v3.0.12 on 64-Bit
Matlab on Windows.

We keep some 32-Bit Matlab + GStreamer-SDK (v0.10.x) in place for
debugging or testing.

-> Tested to work on 32-Bit Matlab with GStreamer 0.10 SDK
-> Tested to work on 64-Bit Matlab with GStreamer-1.4.0 runtime.
Screen: Build for 64-Bit Matlab on Windows with GStreamer-1.4 support.

Screen for 64-Bit Matlab on Windows is now switched to use
GStreamer-1.4.0 or later with the runtime from www.gstreamer.net
instead of the old SDK.

Testing in Windows-7 VM with Matlab R2012a shows that:
- Movie playback works well.
- Movie writing (with/without sound) works well.
- VideoCapture/Recording seems to work well, as far as this can be
judged from only using the videotestsrc plugin, and no real live video
source. GStreamer-1.4.0 ships without any functional real video capture
plugins on Windows, neither ksvideosrc, nor dshowvideosrc, so video
capture is essentially dead for all practical means until the upstream
GStreamer debs provide the required plugins. The Git repo shows that
ksvideosrc has been ported to Windows, but isn’t included in the distro
here. dshowvideosrc porting seems tbd.

-> Screen.mexw64 rebuilt and tested.

-> Also add some more virtual instances of videotestsrc (device indices
90001 - 90023) which show different test ‘pattern’ settings for a bit
more entertainment value.