EMI: Fix turn_rate of voodoo chair

The turn rate for the chair of the voodoo lady is set to 1 in the lua
code which makes the turn animation very slow (> 30s).

Since the rate value of 1 is not used otherwise in GRIM or EMI,
adjust the turn rate in this case.
EMI: Fix display of "dock" video

During the run of the "dock" video (first arrival at melee island) only
a black screen was displayed although the sound did work.
The lua code dims (_dimLevel = 1) the scene before showing a video so
that only the video is visible. GfxOpenGL::drawBitmap sets the current
color according to the dim level before it starts drawing the bitmap:

glColor3f(1.0f - _dimLevel, 1.0f - _dimLevel, 1.0f  - _dimLevel);

If there is no other glColor* call before drawing the video, the current
color stays (0, 0, 0) and the video won't be visible.

The bug fix resets the color to (1.0, 1.0, 1.0) after the drawing of the
bitmap at the end of GfxOpenGL::drawBitmap.