Hi!

To reall, curentlly, guile-dbi use dlopen to load its backends.
So, for Guix we have to set LD_LIBRARY_PATH, which is not desired.

> [...]
> (me:)
>> I think it will be great to introduce a new search path (eg: GUILE_DBD_PATH)
>> in addition to LD_LIBRARY_PATH.  Find the absolute so filepath in it
>> ourself, then pass to dlopen.  
>
> (ludo:)
> Why not, but then it would be redundant with LD_LIBRARY_PATH and
> LTDL_LIBRARY_PATH, which would further complicate the search rules.
>

Yeah, but I just learn that libltdl has a convenient function to do
this..


So, here are patches for using libltdl and a new search path: