The following systems supports dynamic loading using shared libraries: SunOS 4; Solaris 2; SGI IRIX 5 (but not SGI IRIX 4!); and probably all systems derived from SVR4, or at least those SVR4 derivatives that support shared libraries (are there any that don't?).
You don't need to do anything to configure dynamic loading on these
systems — the `configure' detects the presence of the
`<dlfcn.h>' header file and automatically configures dynamic
loading.