Better ultra_simple for Slamtec RPLIDAR on Linux

Improved the ultra_simple program to visualize the samples with GLUT on Linux, tested with Slamtec RPLIDAR A2.

Check out this branch

https://github.com/zhoub/rplidar_sdk/tree/v1.11.0-gl