ParseUtils: Strip trailing carriage return in nextline

This addresses an issue reading LUT files that contain Windows-style line endings. As discussed in the issue thread (#372), this is the "Really Specific Fix" that explicitly checks for a single trailing carriage return after the call to `std::getline`.

I've tested and confirmed that this allows files with Windows line endings to be read by loading a CSP LUT file that contains them using the Python bindings directly (including creating a processor), and also using the `OCIOFileTransform` node in Nuke 8.0v5 (by replacing `libOpenColorIO.so`, `PyOpenColorIO.so`, and all of the Nuke plugin libraries with those built against my bugfix branch).