gstvalue: Tidy initialisation
gstvalue: Tidy initialisation

Use some macros to make our value functions setup a bit
tidier, and micro-optimise a few reallocs by setting an
initial size for the global type arrays.

shelsonjava/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,mparis/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,centricular/gstreamer,jpxiong/gstreamer,mparis/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,jpxiong/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,mparis/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,centricular/gstreamer