On IE (from 9.0 up to at least IE EDGE 14) we have this behavior
for the method serializeToString of XMLSerializer:

> (new XMLSerializer()).serializeToString($('<b>"</b>')[0])
  '<b xmlns="http://www.w3.org/1999/xhtml">"</b>'
> (new XMLSerializer()).serializeToString($('<b>"</b>')[0].firstChild)
  '&quot;'

Whilst browser such as chromium or firefox have:

> (new XMLSerializer()).serializeToString($('<b>"</b>')[0])
  '<b xmlns="http://www.w3.org/1999/xhtml">"</b>'
> (new XMLSerializer()).serializeToString($('<b>"</b>')[0].firstChild)
  '"'

Hence for IE9 and over, if in a `<t t-extend/>` a `t-jquery`
sub-directive (without `t-operation`) is available, we can have
broken javascript if a " is transformed into an &quot; at a unfortunate
location.

This commit favour node.data over XMLSerializer serializeToString to
avoid the possibility of this issue when a text node is processed.

opw-727283