@alexvoronov pointed out that the example was actually wrong.

same as b2b2176c

Fixes #140

I checked that this regtest fails without last commit

Related to #190

No EOL at the end of the file is only tolerated in input file
(e.g. plumed.dat) and not in other files (including HILLS files).

Indeed, when using multiple walkers, it is possible that transiently
the HILLS file from other walkers have incomplete lines.
With this fix, those lines are ignored and read at the next iteration.

This fixes #190

When doxygen is not found, doc is disabled