Impacted versions: ODOO 10

Problem.
If i print a invoice with a negative amount, the pdf shows a vertical bar instead of a minus symbol.
![image](https://cloud.githubusercontent.com/assets/28800797/26237253/b07fadb0-3c74-11e7-86c2-c8688d82b5a5.png)

I have tried to install a new pdf reader, but with no result.
openerp/addons/base/ir/ir_qweb.py
elif trim == 'both':
            inner = inner.strip()
        if name == "t":
            return inner
        elif len(inner) or name not in self._void_elements:
            return "<%s%s>%s</%s>" % tuple(
                qwebcontext if isinstance(qwebcontext, str) else qwebcontext.encode('utf-8')
                for qwebcontext in (name, generated_attributes, inner, name)
            )
        else:
            return "<%s%s/>" % (name.encode("utf-8"), generated_attributes)
    def render_attribute(self, element, name, value, qwebcontext):
        return _build_attribute(name, value)
    def render_text(self, text, element, qwebcontext):
        return text.encode('utf-8')
    def render_tail(self, tail, element, qwebcontext):
        return tail.encode('utf-8')
    
    def render_att_att(self, element, attribute_name, attribute_value, qwebcontext):
        if attribute_name.startswith("t-attf-"):
            return [(attribute_name[7:], self.eval_format(attribute_value, qwebcontext))]
        if attribute_name.startswith("t-att-"):
            return [(attribute_name[6:], self.eval(attribute_value, qwebcontext))]
        result = self.eval_object(attribute_value, qwebcontext)
        if isinstance(result, collections.Mapping):
            return result.iteritems()
        
        return [result]
    
    def render_tag_raw(self, element, template_attributes, generated_attributes, qwebcontext):