move common code file in common directory

remove several unused files
remove mem_block_t that is never used in a different way than a simple heap buffer
move up IP address type and remove duplications of the same struct declaration

openair2/RRC/LTE/L2_interface.c

@@ -36,7 +36,7 @@
  * \email: javier.morgade@ieee.org
  */
 
-#include "platform_types.h"
+#include "common/platform_types.h"
 #include "rrc_defs.h"
 #include "rrc_extern.h"
 #include "common/utils/LOG/log.h"