relative paths can remove scheme from xslt URI

When using relative paths in an XSLT referenced from another one, the used URI scheme may be ignored.

e.g. in case of an XSLT specified by URI "classpath:location/master.xsl",  that includes another one:  <xsl:include href="../child.xsl"/>

In this case, the URI of child.xsl is resolved as just "child.xsl" instead of "classpath:child.xsl", omitting the URI scheme.

The cause is XsltUriResolver, in which FileUtil.compactPath() is used to calculate the relative URI, but this call ignores the colon separator and considers "classpath:location" as a single path part.

I'm creating a pull request which passes the URI without scheme to FileUtil.compactPath().