Initial port to Qt 5.1.0 on OS X.
Fix initial Qt 5 build on Linux.
Fix GPU processing mode for Qt 5.1 on Linux.

The GL render context must be created on the thread in which it will be
used. Then, when the consumer stops, we must tell glsl.manager to
cleanup and destroy the context on the render thread.
Add showPaused() method.

This will be used by FiltersDock when it needs to pause the player/MLT
consumer to keep things stable.
Pause consumer instead of restart when change filters list.

Stopping and restarting the consumer is not so stable on Qt 5 with GPU
processing at this time, and it seems heavier handed than simply
pausing. However, to the user an unexpected pause might seem heavier
handed. :-(
Fix build on OS X and Windows.
A couple tweaks for Qt 5 on OS X.
Let variable MLT_PREFIX define path to MLT dependency on OS X.
GLEW is no longer used.
Fix DockWidgets on Qt 5.1 for OS X.
Add UI Themes and improve support for HDPI (Retina).
Prevent crashes with no playlist.
Fix default preset for frei0r color grading filter.
Fix crash on White Balance filter with GPU.

And fix temporarily disabling filter when using eye dropper and not GPU.
Make generated XML less verbose.
Fix synchronizing pause between MLT and player.

Conflicts:
	src/mainwindow.cpp
Fix thumbnail creation for Qt5 with GPU.

This actually changes it for non-GPU as well. It has changed from using the producer object to building a new producer based on the resource. This will pave the way for caching the thumbnails keyed on URI and in/out point.
Only handle up/down/numeric keys if playlist open.
Do not let timecodes on scrubbar get too close.
Delete main help page instead of hiding it.