GRIM: Fixes #1113
GRIM/EMI: Handle special case in Actor::walkForward()

The walk chore of the monkey bot is simulating
a robotor-like walking style by setting _walkRate to
0.0f repeatedly. This prohibits walking forward
which results in stopping the walk chore eventually.

To avoid the walk chore in this case to stop, assume that
the actor has walked when calling Actor::walkForward() with
a _walkRate of 0.0f.
GRAPHICS: Reset GL's current color in drawDimPlane()

Per convention, in residualvm the default GL current color
should be (1.0f, 1.0f, 1.0f). If a function changes the color,
it is required to reset it before returning.

This fixes the issue that some videos were not correctly displayed
until the next glColor call (e.g. when drawing the sub-titles) was
issued.
Merge pull request #1118 from chkr-private/movie-fixes

GRAPHICS: Reset GL's current color in drawDimPlane()
Merge pull request #1117 from chkr-private/walk-fixes

GRIM/EMI: Handle special case in Actor::walkForward()
GRIM: Only check collision on setPos in EMI

Fixes #1115