So I have cleaned up and I noticed also that when installing all the libs get copied to /usr/local/lib whilst the plugin was looking at /usr/lib. It was necessary to move them to /usr/lib otherwise the plugin could not find the libs. This is also the reason why it was not loading ....
/usr/local/lib is standard unix destination for non-system (non-packaged) libraries. but most ready-made distributions don't include /usr/local/lib in their ldconfig configuration. so either you set LD_LIBRARY_PATH to /usr/local/lib, or you include /usr/local/lib in /etc/ld.so.conf.d/, or (recommended) you set DESTDIR either in Make.config or via an environment variable to /usr when compiling and installing the libraries.
debugging the library:
gdb some_library.so will give absolutely _no_ information (because you can't execute a library).
you'll have to debug the whole vdr process when running:
gdb --args vdr <all the parameters and options and plugin stuff>
gdb --args vdr -P 'graphlcd -d usb_reelfp'
DESTDIR should be set to /usr, not /usr/lib (because the essential variable is LIBDIR, and this one is defined as $(DESTDIR)/lib). i've corrected this typo in the posting.