Improvement: Use select() for main loop

- Back to using select() for main loop. Thus we are not longer relying
  on libevent.

- Add generic timeout system (untested) to prepare for D-Bus support.

- Drop troff man pages. Revise Makefile to improve documentation
  building, fix double LDFLAGS inclusion, and re-add -lrt. This turns
  asciidoc into a build time dependency.

- Change fading time calculation.

- Add --logpath and ostream_reopen() for debugging with -b.

- Drop unused lceil_ntimes() and other helper functions.

- Only very limited tests are done. Bugs to be expected.