gst/realmedia/: Use g_hash_table_destroy instead of _unref which is too new.

gst/realmedia/: Use g_hash_table_destroy instead of _unref which is too new.

Original commit message from CVS:
* gst/realmedia/asmrules.c: (gst_asm_node_free),
(gst_asm_node_evaluate), (gst_asm_scan_new), (gst_asm_scan_free),
(gst_asm_scan_string), (gst_asm_scan_number),
(gst_asm_scan_identifier), (gst_asm_scan_print_token),
(gst_asm_scan_next_token), (gst_asm_rule_free),
(gst_asm_rule_add_property), (gst_asm_scan_parse_operand),
(gst_asm_scan_parse_expression), (gst_asm_scan_parse_condition),
(gst_asm_scan_parse_property), (gst_asm_scan_parse_rule),
(gst_asm_rule_evaluate), (gst_asm_rule_book_new),
(gst_asm_rule_book_n_rules), (gst_asm_rule_book_free),
(gst_asm_rule_book_match), (main):
* gst/realmedia/rtspreal.c: (rtsp_ext_real_parse_sdp),
(rtsp_ext_real_stream_select), (gst_rtsp_real_plugin_init):
Use g_hash_table_destroy instead of _unref which is too new.