ext/libmng/: Somewhat port mngenc and mngdec to 0.10. Does not work yet and has many bits ifdeffed out still.

Original commit message from CVS:
* ext/libmng/Makefile.am:
* ext/libmng/gstmng.c: (plugin_init):
* ext/libmng/gstmngdec.c: (gst_mng_dec_base_init),
(gst_mng_dec_class_init), (gst_mng_dec_sink_setcaps),
(gst_mng_dec_init), (gst_mng_dec_src_getcaps), (gst_mng_dec_loop),
(gst_mng_dec_get_property), (gst_mng_dec_set_property),
(mngdec_error), (mngdec_openstream), (mngdec_closestream),
(gst_mng_dec_sink_event), (mngdec_readdata), (mngdec_settimer),
(mngdec_processheader), (mngdec_getcanvasline), (mngdec_refresh),
(gst_mng_dec_change_state):
* ext/libmng/gstmngdec.h:
* ext/libmng/gstmngenc.c: (gst_mng_enc_base_init),
(gst_mng_enc_class_init), (gst_mng_enc_sink_setcaps),
(gst_mng_enc_init), (gst_mng_enc_chain),
(gst_mng_enc_get_property), (gst_mng_enc_set_property):
* ext/libmng/gstmngenc.h:
Somewhat port mngenc and mngdec to 0.10. Does not work yet and has many
bits ifdeffed out still.