remove nvidiahack lib

1. it apparently is ineffective
2. if it was effective, it's current behavior would be not exactly helpful
(sets __GL_YIELD to NOTHING, causing busy waits on doublebuffer swapping)
3. it does for sure pollute the doublebuffer/usleep detection (setenv is set to override),
ie. the overehad detection code gets a different opinion on __GL_YIELD than libGL

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