Fix various problems in 4G NAS handling

- rename as_nas_info_t member data to nas_data to have a uniq name to
  trace between complex malloc/free of this pointer
- fix, maybe not perfect, these pais od malloc/free
- remove typedef name changes across transmission of these as_nas_info_t
  over itti, as name changing makes it even more confusing
- remove globals that are likely possible races
- in as_message_decode() fix memcpy size, it is hard to understand the
  initial idea, likely the author beleives a struct of struct makes a
  intermediate pointer
- in network_api.c remove globals (static but used globally)
- remove casts that are there to hide gcc warnings on probable unaligned
  access
- remain a weird mix of packed/unpacked versions of the same typedef,
  but gcc is happy

openair2/COMMON/as_message.h

@@ -167,7 +167,7 @@ typedef struct as_stmsi_s {
 /* Dedicated NAS information */
 typedef struct as_nas_info_s {
   uint32_t length;    /* Length of the NAS information data       */
-  Byte_t* data;   /* Dedicated NAS information data container */
+  Byte_t* nas_data; /* Dedicated NAS information data container */
 } as_nas_info_t;
 
 /* Radio Access Bearer identity */