Description of "--with-dlopen" in "./configure" output is confusing

In v9.16, the description of --with-dlopen is:

  --with-dlopen=ARG       support dynamically loadable DLZ and DYNDB drivers

In ~"v9.11", it is:

  --with-dlopen=ARG       support dynamically loadable DLZ drivers

The problem is that the option controls more than that - specifically, if it is set to auto (default) or yes, it triggers the following call:

	  AC_SEARCH_LIBS([dlsym],[dl])

which means: "if the dlsym() function is found in libdl, append -ldl to LIBS".

This means that --with-dlopen does not just control whether DLZ/dyndb drivers will be built - it also detects whether the platform supports dlopen(). In other words, if --without-dlopen is used, -ldl will not be automatically added to LIBS, which means the platform will be treated as if dlopen() was unavailable on it.

This has consequences when certain combinations of ./configure switches are used - should --enable-native-pkcs11 --without-dlopen work or not?

• If --without-dlopen only controls building DLZ/dyndb drivers, as claimed by ./configure, then the above combination of switches should work - PKCS#11 has little to do with DLZ/dyndb. Yet, such a build breaks on PKCS#11 unit tests which do require dlopen() support (d'oh!) but -ldl is not in their LIBS.

• If --without-dlopen is also meant to mean "forcibly disable dlopen() support", then the above combination of switches should be prohibited at ./configure time as it does not make sense (PKCS#11 is all about dynamically loading "providers" in the form of shared objects).

In v9.16, the situation only gets more convoluted because - at least on Linux - pkg-config --libs libuv returns... -luv -ldl.

Plugins are also not mentioned in the output of ./configure in v9.16.

We need to decide whether we want to:

• revise the description of --with-dlopen in ./configure, keeping configure.ac code as it is,

• revise configure.ac so that detection of dlopen() support in the operating system is decoupled from detection of the toolchain's capabilities of building dlopen()able objects.