update Changelog.txt, thirdparty/versions.txt and release date.
Update Greek translation.

refs PR 76
MP4Splitter: fixed playback for same 3gp with AMR sound (fixed 4496) (ticket #3079)
Audio Switcher: Improve normalization algorithm.

Use a much better regain strategy (similar to ffdshow's) and fix the regain rate to be linear rather than completely exponential.

This commit fixes #1936.
Audio switcher: Use percentage instead of dB for the boost.

Internally a percentage was already used and it is much easier for the user to understand a boost expressed in percentage.
Audio Switcher: Add a setting to change the max normalization factor.

Use a max normalization factor of 4 by default instead of 10 to avoid huge volume variations.

Refs: #1936.
Bump version to 1.6.8.
run astyle
update lcms to 5bf9e43
Updated Simplified Chinese translation.
VMROSD: Allow the seekbar to be hidden and the video window to be changed after the OSD has started.
This is done in preperation of D3DFullscreen switching.
Allow the user to switch between D3DFullscreen and windowed mode on the fly.

This allows D3DFullscreen to exit like regular fullscreen.
Make it crash less.

Time to refactor the code to take into account that the application can exit D3D fullscreen.
SetVideoWindow shouldn't reset the device, let SetFullscreen do it instead.
Improve D3DFullscreenToggle enable code
VMROSD: Update the OSD bitmap after setting a new video window.
Show the cursor when exiting D3DFullscreen
Escape now also enables fullscreen