Define a 0 and -1 step amount. They used to almost do the same thing but now, 0 cancels/stops the current step and -1 keeps on stepping until the end of the segment. See https://bugzilla.gnome.org/show_bug.cgi?id=679378
https://bugzilla.gnome.org/show_bug.cgi?id=658449
Unify the ad-hoc markup to be asciidoc style in many places. Add a "html" target to Makefile to generate the output.