Fix test 'tour'.

Executing 'tour' test now creates some files in /tmp to store the
revision numbers as they are created on the fly and appear in the output
files. When SVG files are to be converted to PNG or EPS files within the
Makefile, a tool 'fixsvg' will be invoked to substitute some placeholder
markup by the real version number which fits to the test output, before
the final conversion takes place.