Backported only the softlink part of the patch,
*not* the bumping of library version.

With this patch, the libmysql/ directory contains:
libmysqlclient.a
libmysqlclient_r.a -> libmysqlclient.a
libmysqlclient_r.so -> libmysqlclient.so*
libmysqlclient_r.so.18 -> libmysqlclient.so.18*
libmysqlclient_r.so.18.0.0 -> libmysqlclient.so.18.0.0*
libmysqlclient.so -> libmysqlclient.so.18*
libmysqlclient.so.18 -> libmysqlclient.so.18.0.0*
libmysqlclient.so.18.0.0*