Hard-code COPR project names and switch them as well as prefix Release
tag based on mode.  This prevents from confusing builds.

Most of the time we want to anyway, and it's easy to interrupt if
needed.

It was moved to slop subdirectoty in attempt to get rid of rpmlint
warning concerning non-standard soname:  this would make 'libslopy.so' a
"private" library, for which naming is not mandatory.

However, this actually breaks slop binary!

Turns out there's no way around it.  What we could do is, in order of
preference:

 1. Solve naming issue with upstream.

 2. Just call it libslopy.so.1.

 3. Use wrapper to add %{_libdir}/slop to LD_LIBRARY_PATH

(The last thing seems really like a too hacky for such simple utility.)

Since libslopy is considered private, there should not be need for
header file.