Use -release instead of -version-info for internal library SONAMEs

Use -release instead of -version-info for internal library SONAMEs

The BIND 9 libraries are considered to be internal only and hence the
API and ABI changes a lot.  Keeping track of the API/ABI changes takes
time and it's a complicated matter as the safest way to make everything
stable would be to bump any library in the dependency chain as in theory
if libns links with libdns, and a binary links with both, and we bump
the libdns SOVERSION, but not the libns SOVERSION, the old libns might
be loaded by binary pulling old libdns together with new libdns loaded
by the binary.  The situation gets even more complicated with loading
the plugins that have been compiled with few versions old BIND 9
libraries and then dynamically loaded into the named.

We are picking the safest option possible and usable for internal
libraries - instead of using -version-info that has only a weak link to
BIND 9 version number, we are using -release libtool option that will
embed the corresponding BIND 9 version number into the library name.

That means that instead of libisc.so.1701 (as an example) the library
will now be named libisc-9.17.10.so.