add vala back compatibility

vala 0.16 doesn't like commas at the last array element
add gstreamer-1.0.vapi

vala 0.16 doesn't include gstreamer-1.0.vapi

This patch add a directory called vapi/ with the gstreamer-1.0 vapi. In order
to enable this vapi directory, the user should compile

$ make OLDVALA=1
enum types generation
View.display_notification() is static

Hence we can call it, even without instanciate the View class, something that
occurs when Opal fails.