ZMQ radio

This commit introduces ZMQ-based radio library. Each pair of RX/TX antennas is
represented by a ZMQ REQ/REP socket pair which streams continuous IQ samples
from radio start until stop.

Usage:
Simplest configuration is to connect OAI NR UE to OAI GNB with the same number
of antennas - by inverting the RX and TX channels in ZMQ radio configuration the
gNBs TX is mapped to UEs RX antennas and vice versa.

common/config/config_load_configmodule.c

@@ -282,12 +282,9 @@ configmodule_interface_t *load_configmodule(int argc,
       cfgmode = strdup(CONFIG_LIBCONFIGFILE);
     }
   }
-  static configmodule_interface_t *cfgptr = NULL;
-  if (cfgptr)
-    fprintf(stderr, "ERROR: Call load_configmodule more than one time\n");
 
   // The macros are not thread safe print_params and similar
-  cfgptr = calloc(sizeof(configmodule_interface_t), 1);
+  configmodule_interface_t *cfgptr = calloc(sizeof(configmodule_interface_t), 1);
   if (!cfgptr) {
     fprintf(stderr, "ERROR: cannot allocate a memory for configuration\n");
     return NULL;