[RFC] Cleanup user documentation build

This PR does some cleanup in the Makefile of the user documentation.
The first commit makes `make html` work.
Also some generated files got deleted and the `*.1` files are converted to UTF-8.
Only `.1`files are installed. Most of the system default are ascii and some latin-1, and the few which are utf-8 get rendered incorrectly:
https://developer.apple.com/library/prerelease/mac/documentation/Darwin/Reference/ManPages/man1/mmroff.1.html (see Author section)
It seems that utf-8 manages are not supported in OS X.