Handle spaces in URIs

[drmacro]

From Radu Coravu:

One more suggestion to make mathml refs properly work even when the mathml equation is in a folder structure with spaces in it.
In the file relpath_util.xsl the function "relpath:toUrl" should be slightly modified like:

        <xsl:function name="relpath:toUrl" as="xs:string">
            <xsl:param name="filepath" as="xs:string"/>
            <xsl:variable name="url" as="xs:string"
                select="if (contains($filepath, '\'))
                then translate($filepath, '\', '/')
                else $filepath
                "
            />
            <xsl:variable name="fileUrl" as="xs:string"
                select="
                if (matches($url, '^[a-zA-Z]:'))
                then concat('file:/', $url)
                else if(starts-with($url, '/')) then concat('file:', $url) else $url"
            />
            <xsl:sequence select="replace($fileUrl, ' ', '%20')"/>
        </xsl:function>

so that it does two extra things:

1. If the initial URL fragment starts with "/", it means it is a Linux file path and we need to prepend file: to it.
2. Replace simple spaces with url encoded version.

This worked for me.

[drmacro]

Fix committed on develop branch.