gst/rtp/: Added MP4A-LATM payloader to match the depayloader.

gst/rtp/: Added MP4A-LATM payloader to match the depayloader.

Original commit message from CVS:
* gst/rtp/Makefile.am:
* gst/rtp/gstrtp.c: (plugin_init):
* gst/rtp/gstrtpmp4apay.c: (gst_rtp_mp4a_pay_get_type),
(gst_rtp_mp4a_pay_base_init), (gst_rtp_mp4a_pay_class_init),
(gst_rtp_mp4a_pay_init), (gst_rtp_mp4a_pay_finalize),
(gst_rtp_mp4a_pay_parse_audio_config), (gst_rtp_mp4a_pay_new_caps),
(gst_rtp_mp4a_pay_setcaps), (gst_rtp_mp4a_pay_handle_buffer),
(gst_rtp_mp4a_pay_change_state), (gst_rtp_mp4a_pay_plugin_init):
* gst/rtp/gstrtpmp4apay.h:
Added MP4A-LATM payloader to match the depayloader.