ext/jpeg/gstjpegdec.*: API: Added IDCT method property

ext/jpeg/gstjpegdec.*: API: Added IDCT method property

Original commit message from CVS:
* ext/jpeg/gstjpegdec.c: (gst_idct_method_get_type),
(gst_jpeg_dec_class_init), (gst_jpeg_dec_init),
(gst_jpeg_dec_decode_indirect), (gst_jpeg_dec_decode_direct),
(gst_jpeg_dec_chain), (gst_jpeg_dec_sink_event),
(gst_jpeg_dec_set_property), (gst_jpeg_dec_get_property):
* ext/jpeg/gstjpegdec.h:
API: Added IDCT method property
Small cleanups.
Avoid dynamic allocation of trivial fixed structure.
Allocate enough space for temp 4:4:4 YUV buffers. Fixes #343661.