WBXML: add a basic sanity check for offset overflow

This is a naive approach allowing to detact that something went wrong,
without the need to replace all proto_tree_add_text() calls as what was
done in master-2.0 branch.

Bug: 12408
Change-Id: Ia14905005e17ae322c2fc639ad5e491fa08b0108
Reviewed-on: https://code.wireshark.org/review/15310
Reviewed-by: Michael Mann <mmann78@netscape.net>
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
dissect_wbxml(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	dissect_wbxml_common(tvb, pinfo, tree, NULL);
}

dissect_wbxml(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
	dissect_wbxml_common(tvb, pinfo, tree, NULL);
}
