Make res_all a static variable.

Also make the msgs resource config items a static array in the different
config parsers of the daemons and no longder some global variable that
is exported from the shared library. Jobdefs are now expanded using a
dedicated function in src/dird/dird_conf.c
Drop an unneeded global variable and make it local.
Remove old global variable.
Rework dlopen of plugins.

Allow plugins to do lazy symbol binding when loading and allow
the symbols to be global so in the python plugins we can load the
dynload modules which are not linked against libpython. Otherwise
we get symbol errors on load.
Tweak windows dlopen code.
Rebuild configure and config.h.in
Allow to disable client in client configuration

Fixes #288: Disable client in client configuration