gst/smpte/: Add new plugin that adds the SMPTE transition in the alpha channel of

gst/smpte/: Add new plugin that adds the SMPTE transition in the alpha channel of

Original commit message from CVS:
* gst/smpte/Makefile.am:
* gst/smpte/gstsmpte.c: (gst_smpte_plugin_init):
* gst/smpte/gstsmpte.h:
* gst/smpte/gstsmptealpha.c:
(gst_smpte_alpha_transition_type_get_type),
(gst_smpte_alpha_get_type), (gst_smpte_alpha_base_init),
(gst_smpte_alpha_class_init), (gst_smpte_alpha_update_mask),
(gst_smpte_alpha_setcaps), (gst_smpte_alpha_get_unit_size),
(gst_smpte_alpha_init), (gst_smpte_alpha_finalize),
(gst_smpte_alpha_do_ayuv), (gst_smpte_alpha_do_i420),
(gst_smpte_alpha_transform), (gst_smpte_alpha_set_property),
(gst_smpte_alpha_get_property), (gst_smpte_alpha_plugin_init):
* gst/smpte/gstsmptealpha.h:
* gst/smpte/plugin.c: (plugin_init):
Add new plugin that adds the SMPTE transition in the alpha channel of
I420 and AYUV frames so that they can be blended with videomixer later
on. Uses all niceties such as using base transform for efficient alloc
and negotiation. It currently requires GstController to control the
position in the transition effect.