With previous commit, the following data types are generated in ProtocolIE-Field.h
for S1AP's ASN.1 :

```
typedef enum ProtocolIE_Field_6564P0__value_PR {
    ProtocolIE_Field_6564P0__value_PR_NOTHING, /* No components present */
    ProtocolIE_Field_6564P0__value_PR_E_RABToBeSetupItemBearerSUReq
} ProtocolIE_Field_6564P0__value_PR;

typedef struct ProtocolIE_Field_6564P0 {
    ProtocolIE_ID_t      id;
    Criticality_t        criticality;
    struct ProtocolIE_Field_6564P0__value {
        ProtocolIE_Field_6564P0__value_PR        present;
        union ProtocolIE_Field_6564P0__value_u {
            E_RABToBeSetupItemBearerSUReq_t      E_RABToBeSetupItemBearerSUReq;
        } choice;

        /* Context for parsing across buffer boundaries */
        asn_struct_ctx_t _asn_ctx;
    } value;

    /* Context for parsing across buffer boundaries */
    asn_struct_ctx_t _asn_ctx;
} ProtocolIE_Field_6564P0_t;

```

It's difficult for developer to recognize to which ASN.1 type they are linked.
They all start with 'ProtocolIE_Field_'. It will be error-prone.

With this commit, more human comprehensible data types are generated :

```

typedef enum E_RABToBeSetupItemBearerSUReqIEs__value_PR {
    E_RABToBeSetupItemBearerSUReqIEs__value_PR_NOTHING, /* No components present */
    E_RABToBeSetupItemBearerSUReqIEs__value_PR_E_RABToBeSetupItemBearerSUReq
} E_RABToBeSetupItemBearerSUReqIEs__value_PR;

typedef struct E_RABToBeSetupItemBearerSUReqIEs {
    ProtocolIE_ID_t      id;
    Criticality_t        criticality;
    struct E_RABToBeSetupItemBearerSUReqIEs__value {
        E_RABToBeSetupItemBearerSUReqIEs__value_PR present;
        union E_RABToBeSetupItemBearerSUReqIEs__value_u {
            E_RABToBeSetupItemBearerSUReq_t               E_RABToBeSetupItemBearerSUReq;
        } choice;

        /* Context for parsing across buffer boundaries */
        asn_struct_ctx_t _asn_ctx;
    } value;

    /* Context for parsing across buffer boundaries */
    asn_struct_ctx_t _asn_ctx;
} E_RABToBeSetupItemBearerSUReqIEs_t;

```

Developers can understand they are generated from :

```

E-RABToBeSetupItemBearerSUReqIEs S1AP-PROTOCOL-IES ::= {
    { ID id-E-RABToBeSetupItemBearerSUReq CRITICALITY reject TYPE E-RABToBeSetupItemBearerSUReq PRESENCE mandatory },
    ...
}

```