libfprint already uses G_DEBUG_HERE in a lot of places which requires
GLib 2.50. Also add the appropriate defines so that usage of newer API
will result in warnings.
The upekts driver needs upek_proto.c while the upektc driver does not.
Move the corresponding source file entries so that both drivers compile
standalone.
The only API user currently seems to be the examples. fprintd has its
own storage and that will be a good idea in general.
So deprecate the API, we'll need to find a different solution for the
examples eventually.
The function was committed by accident as part of commit d18e1053
(lib: Add a way to name timeouts). It is not used anywhere and
fpi_timeout_cancel_all_for_dev exists, is exported and used and serves
the same purpose.
