Fix an exception on wx-3.0-gtk3 in PLCOpenEditor when generating ST files.

On Python2.7 with WX3.0 and GTK3, an assertionError rises on generating a ST file if the name is already set. The first generation works without problems, if you generate the file a second one, PLCOpenEditor tries to open the file
save dialog with the pre entered name from last run. Then the following assertion pops up:

PyAssertionError: C++ assertion "volDummy.empty() && pathDummy.empty()" failed at ./src/common/filename.cpp(568) in Assign(): the file name shouldn't contain the path

This fix reduces the filepath of the ST file the to the filename. Now it works fine.

include yslt.yml2

in xsl {
    decl istylesheet (
        *output="xml",
        version="1.0",
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform",
        xmlns:exsl='http://exslt.org/common',
        extension-element-prefixes='exsl'
    ) alias stylesheet {
        output *output;
        content;
    };

    decl template(match) {
        content;
    };

    decl function(name) alias template {
        content;
    };
   
    decl call(name) alias call-template {
        content;
    };

    decl apply(select) alias apply-templates {
        content;
    };
}