Thanks for the patch Xavier. It works fine.

I hadn't realised that httrack plugin modules are loaded just like any
"normal" shared library. In that case, if they are to be searched for on the
LD_LIBRARY_PATH, might it be a good idea for them to all have "httrack" or
"hts" in their name? With names like 'libfilename' and 'liblog' it wouldn't be
very surprising if other libraries with those names  existed...

Alternatively, to save having to put these things onto the LD_LIBRARY_PATH,
the configure script could define (and pass through to gcc -D) the library
path according to where they will actually be installed, and the plugin loader
would refer to this path; then the genericness of the filenames wouldn't
matter so much.