Commit
7ebcb041f2ce887ef4d1a64607558889a86ff169
by stevelib: set SOVERSION back to 0
When the version was incremented to 2.0.0, this resulted
in the SOVERSION being set to 2, indicating an ABI change,
which was actually not the case.
People have been complaining that software linked against
librtlsdr.so.0 is no longer working, so change the SOVERSION
back to 0.