pls: don't use GTimeVal on newer glib
pls: don't use GTimeVal on newer glib

On 2.62.0 we can use new API and avoid GTimeVal usage in grl-pls.c. As
2.62 is a bit new, wrap the old code to avoid warnings on new builds.
It can be removed after bumping glib to >= 2.62.0

GNOME/grilo,GNOME/grilo