this allows requesting global/local symboling for loading shared objects;
previously this was system-dependent, now it is _requested_ as "local" for all environments
config/runtime.cfg: add COB_LOAD_GLOBAL
libcob:
* call.c (cob_dlopen): new function used instead of partially re-defining lt_dlopen; changed default to not load symbols to the global namespace any more but locally (was always the case for _WIN32)
* common.c, coblocal.h (cob_settings): added boolean COB_LOAD_GLOBAL to toggle into which namespace the symbols of CALLed programs should be made available
* call.c (cob_dlopen, add_to_preload, cache_preload, cob_exit_call): handle COB_LOAD_GLOBAL (load_global)