Git-Master Merge Request #4: Make guvicview skips device files for metadata. (merged)

Since Linux kernel v4.15, guvcview's device list displays duplicated devices shown as the following image:

Recent linux kernel provides two device files for each video capture device - one is for the usual device handling and the other one is for retrieving metadata. Because guvcview does not utilze the metadata, you could drop them from the device list.

This patch solves this issue. It makes guvcview to check the video capturing capability of each device.