Qt on Raspberry Pi guide updated

Qt 5.10.1 qmake

The tutorial on building Qt 5.10 on Raspberry Pi has been tested and checked, added more details on optional packages and a workaround for issues with Broadcom OpenGL librarie filenames on default installations. The same instructions have also been tested on the latest version, 5.11.1 and found to work just fine (just adjust version in downloads and commands!).