Revert "UbuntuDrivers/detect.py, _check_video_abi_compat(): Disable NVidia driver if X.org's log shows that the Intel driver is loaded. This prevents breaking hybrid systems as long as the NVidia driver and X.org do not work on those."

This reverts commit d3cdf2515c78f4ead0571567f6f04b85fbf59ee0.

Enable installing graphics drivers on Hybrid systems. Also remove the relevant test.
gpu-manager.c: make the third argument of act_upon_module_with_params() non constant
gpu-manager.c: add missing return type to find_string_in_file()
Releasing 1:0.2.89