[Libosinfo] [libosinfo 0/3] Add osinfo_platform_get_all_devices()

[Christophe Fergeau]

This patch series adds a osinfo_platform_get_all_devices() method
similar to what osinfo_os_get_all_devices() does.
To avoid duplicating most of osinfo_os_get_all_devices(), the series
starts by adding a helper that will be used by both methods.

Christophe