Finding shared library at run-time

[Benjamin Kosnik]

Hmm. This doesn't work on x86/linux. I've backed it out. 

These are the options:

   - add LIBDIR to the `LD_LIBRARY_PATH' environment variable
     during execution
   - add LIBDIR to the `LD_RUN_PATH' environment variable
     during linking
   - use the `-Wl,--rpath -Wl,LIBDIR' linker flag

All the other bits are in though.

thanks,
benjamin