r11377: Add support for building LIBRARY elements as shared libraries:

r11377: Add support for building LIBRARY elements as shared libraries:
 - Adds -rpath bin/ so you don't have to install Samba in order to use compiled binaries.
 - Writes out pkg-config files when building shared libs
 - Supports automatic fallback to MERGEDOBJ (which is the default) or
   OBJ_LIST (if ld -r is not supported)

Building with shared libs reduces the size of the Samba binaries from
197 Mb to 60 Mb (including libraries) on my system (GCC4, with debugging).

To build with shared libraries support enabled, run:

LIBRARY_OUTPUT_TYPE=SHARED_LIBRARY ./config.status

init functions don't get called correctly yet when using shared libs, so
you won't be able to actually run anything with success :-)

Once init functions are done, I'll look at support for loading shared
modules once again.

Based on a patch by Peter Novodvorsky (nidd on IRC).