Without this, rpmlint (on openSUSE Tumbleweed) fails with:
librgw2.x86_64: E: shlib-policy-name-error (Badness: 10000) librgw1
Your package contains a single shared library but is not named
after its SONAME.
It seems that the VERSION/SOVERSION mismatch results in the
creation of librgw.so.1 and librgw.so.2.0.0, whereas it should
be librgw.so.2 and librgw.so.2.0.0.