Fix expension of macros in pointers with default values.

For example :

in xsl decl widget_class(%name, *clsname="%nameWidget", match="widget[@type='%name']", mode="widget_class") alias template {
| class `text **clsname` extends Widget{
content;
| }
};

widget_class('Input');

gives now :

<xsl:template match="widget[@type='Input']" mode="widget_class">
<xsl:text>class </xsl:text>
<xsl:text>InputWidget</xsl:text>
<xsl:text> extends Widget{
</xsl:text>
<xsl:text>}
</xsl:text>
</xsl:template>

Without the fix, <xsl:text>InputWidget</xsl:text> would be <xsl:text>%nameWidget</xsl:text>

include homepage.en.yhtml2

page "Hello, world" {
    p   >>
        Hello, world! I can link here, say:
        ¬http://en.wikipedia.org to Wikipedia¬
        >>

    p   >>
        This is ƒemphasized. And this is «code».
        >>
}