ext/amrnb/: Ported AMR decoder/parse.

ext/amrnb/: Ported AMR decoder/parse.

Original commit message from CVS:
* ext/amrnb/Makefile.am:
* ext/amrnb/amrnb.c: (plugin_init):
* ext/amrnb/amrnbdec.c: (gst_amrnbdec_init),
(gst_amrnbdec_setcaps), (gst_amrnbdec_chain),
(gst_amrnbdec_state_change):
* ext/amrnb/amrnbdec.h:
* ext/amrnb/amrnbenc.c: (gst_amrnbenc_get_type),
(gst_amrnbenc_base_init), (gst_amrnbenc_class_init),
(gst_amrnbenc_init), (gst_amrnbenc_finalize),
(gst_amrnbenc_setcaps), (gst_amrnbenc_chain),
(gst_amrnbenc_state_change):
* ext/amrnb/amrnbenc.h:
* ext/amrnb/amrnbparse.c: (gst_amrnbparse_init),
(gst_amrnbparse_query), (gst_amrnbparse_event),
(gst_amrnbparse_chain), (gst_amrnbparse_read_header),
(gst_amrnbparse_loop), (gst_amrnbparse_sink_activate),
(gst_amrnbparse_state_change):
* ext/amrnb/amrnbparse.h:
Ported AMR decoder/parse.
Added AMR encoder.