Fix a lot of HTML-generation bugs by implementing some additional macros, escape sequences, etc, etc.

Also start to make the code more readable and introduce more Qt/C++
while eliminating old C code, which is horrible to maintain.

The request keywords are now looked up by a gperf hash function.
The generated gperf file is committed, so that noone has to rely on the existence of gperf on the build machine.

If I broke the rendering of some man pages, please inform me.