Add jp2k plugin. Fixes #550657.

Add jp2k plugin.  Fixes #550657.

Original commit message from CVS:
* configure.ac:
* ext/Makefile.am:
* ext/jp2k/Makefile.am:
* ext/jp2k/gstjasperdec.c: (gst_jasper_dec_base_init),
(gst_jasper_dec_class_init), (gst_jasper_dec_init),
(gst_jasper_dec_reset), (gst_jasper_dec_sink_setcaps),
(gst_jasper_dec_negotiate), (gst_jasper_dec_get_picture),
(gst_jasper_dec_chain), (gst_jasper_dec_set_property),
(gst_jasper_dec_get_property), (gst_jasper_dec_change_state),
(plugin_init):
* ext/jp2k/gstjasperdec.h:
Add jp2k plugin.  Fixes #550657.