No general way to determine provider

[whit-schonbein]

There is no general way to select a provider. For example, the various tests either do not specify a provider (rofi_init();) or assume "verbs" (rofi_init("verbs",NULL);).

This can obviously be fixed for a specific platform if the text string name of the provider is known for that system. Alternatively, should there be a general purpose way for a ROFI application to selecting a provider?