Impacted versions: Odoo 11 on windows server 2012

Steps to reproduce: 
Create a new out invoice, select a product and set a negative amount for unit price.
Print the invoice.

Current behavior:
in PDF the char "-" is shown as "|" even if the total amount is correct (amount1 - amount2 = total)

Expected behavior:
the printed invoice should show the char "-"

Video/Screenshot link (optional):
![image](https://user-images.githubusercontent.com/37513316/42877323-8c712b2e-8a89-11e8-9690-27f00e08b6b2.png)

this is the negative item on odoo:
![image](https://user-images.githubusercontent.com/37513316/42877389-bf04eba2-8a89-11e8-91c0-e38059673b42.png)


openerp/addons/base/ir/ir_qweb.py
if not display_currency:
            display_currency = self.display_currency(cr, uid, options['display_currency'], options)
        
        
        
        
        
        fmt = "%.{0}f".format(display_currency.decimal_places)
        from_amount = record[field_name]
        if options.get('from_currency'):
            from_currency = self.display_currency(cr, uid, options['from_currency'], options)
            from_amount = Currency.compute(cr, uid, from_currency.id, display_currency.id, from_amount)
        lang_code = context.get('lang') or 'en_US'
        lang = self.pool['res.lang']
        formatted_amount = lang.format(cr, uid, [lang_code],
            fmt, Currency.round(cr, uid, display_currency, from_amount),
            grouping=True, monetary=True).replace(r' ', u'\N{NO-BREAK SPACE}').replace(r'-', u'\u2011')
        pre = post = u''
        if display_currency.position == 'before':
            pre = u'{symbol}\N{NO-BREAK SPACE}'
        else:
            post = u'\N{NO-BREAK SPACE}{symbol}'
        return HTMLSafe(u'{pre}<span class="oe_currency_value">{0}</span>{post}'.format(
            formatted_amount,
            pre=pre, post=post,
        ).format(
            symbol=display_currency.symbol or '',
        ))
    def display_currency(self, cr, uid, currency, options):