Bugfix [#36950] Restrict Frame Range not being obeyed on Driver F-Curves

By default, drivers (used to) automatically map the driver result (i.e.
"evaltime" or the x-coordinates in the driver graphs) to results. This evaltime
=> cvalue mapping is necessary when there are absolutely no keyframes or
modifiers on a driver F-Curve, or else nothing would happen.

However, when there are modifiers on these driver F-Curves, and these modifiers
only work within certain ranges, there would be confusing and unwanted
situations where even if you clamped the modifiers to only generating a curve
within certain frame ranges, the final driver output would still ignore the
results of the curve due to the underlying 1-1 mapping.

This commit introduces a check to ensure that this automatic mapping won't
happen during such invalid ranges.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@61077 954f8c5b-7b00-dc11-b283-0030488c597c