gst/rtp/: Added G726 pay/depayloaders. Fixes #538891.

gst/rtp/: Added G726 pay/depayloaders. Fixes #538891.

Original commit message from CVS:
Patch by: mersad <mersad at axis dot com>
* gst/rtp/Makefile.am:
* gst/rtp/gstrtp.c: (plugin_init):
* gst/rtp/gstrtpg726depay.c: (gst_rtp_g726_depay_base_init),
(gst_rtp_g726_depay_class_init), (gst_rtp_g726_depay_init),
(gst_rtp_g726_depay_setcaps), (gst_rtp_g726_depay_process),
(gst_rtp_g726_depay_plugin_init):
* gst/rtp/gstrtpg726depay.h:
* gst/rtp/gstrtpg726pay.c: (gst_rtp_g726_pay_base_init),
(gst_rtp_g726_pay_class_init), (gst_rtp_g726_pay_init),
(gst_rtp_g726_pay_setcaps), (gst_rtp_g726_pay_plugin_init):
* gst/rtp/gstrtpg726pay.h:
Added G726 pay/depayloaders. Fixes #538891.