There will be two selector functions generated for the following ASN.1 excerpt.

InitiatingMessage ::= SEQUENCE {
    procedureCode S1AP-ELEMENTARY-PROCEDURE.&procedureCode     ({S1AP-ELEMENTARY-PROCEDURES}),
    criticality   S1AP-ELEMENTARY-PROCEDURE.&criticality       ({S1AP-ELEMENTARY-PROCEDURES}{@procedureCode}),
    value         S1AP-ELEMENTARY-PROCEDURE.&InitiatingMessage ({S1AP-ELEMENTARY-PROCEDURES}{@procedureCode})
}

This pull request enables different function names by adding field name after type name.

For example, there are many 'enum value_PR' and 'struct value' generated if
a class is instantiated as many instances.

typedef enum value_PR {
    value_PR_NOTHING,    /* No components present */
    .....
} value_PR;

typedef struct ProtocolIE_Field_6563P5 {
    ....
    struct value {
        value_PR present;
        union value_u {
        } 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_6563P5_t;

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

result in 'FATAL: Information Object Set E-RABToBeSetupItemBearerSUReqIEs contains no objects at line xxxx'

If it contains more than one entry then there is no problem.

E-RABSetupRequestIEs S1AP-PROTOCOL-IES ::= {
    { ID id-MME-UE-S1AP-ID                  CRITICALITY reject  TYPE MME-UE-S1AP-ID                     PRESENCE mandatory }|
    { ID id-eNB-UE-S1AP-ID                  CRITICALITY reject  TYPE ENB-UE-S1AP-ID                     PRESENCE mandatory }|
    { ID id-uEaggregateMaximumBitrate       CRITICALITY reject  TYPE UEAggregateMaximumBitrate          PRESENCE optional  }|
    { ID id-E-RABToBeSetupListBearerSUReq   CRITICALITY reject  TYPE E-RABToBeSetupListBearerSUReq      PRESENCE mandatory },
    ...
}

One of the most tricky ASN.1 excerpt :

E-RABDataForwardingItemIEs S1AP-PROTOCOL-IES ::= {
    { ID id-E-RABDataForwardingItem   CRITICALITY ignore   TYPE E-RABDataForwardingItem PRESENCE mandatory },
    ...
}

E-RABSubjecttoDataForwardingList ::= E-RAB-IE-ContainerList { {E-RABDataForwardingItemIEs} }

E-RAB-IE-ContainerList { S1AP-PROTOCOL-IES : IEsSetParam } ::=
    ProtocolIE-ContainerList { 1, maxnoofE-RABs, {IEsSetParam} }

ProtocolIE-ContainerList {INTEGER : lowerBound, INTEGER : upperBound, S1AP-PROTOCOL-IES : IEsSetParam} ::=
    SEQUENCE (SIZE (lowerBound..upperBound)) OF
    ProtocolIE-SingleContainer {{IEsSetParam}}

ProtocolIE-SingleContainer {S1AP-PROTOCOL-IES : IEsSetParam} ::=
    ProtocolIE-Field {{IEsSetParam}}

ProtocolIE-Field {S1AP-PROTOCOL-IES : IEsSetParam} ::= SEQUENCE {
    id          S1AP-PROTOCOL-IES.&id           ({IEsSetParam}),
    criticality S1AP-PROTOCOL-IES.&criticality  ({IEsSetParam}{@id}),
    value       S1AP-PROTOCOL-IES.&Value        ({IEsSetParam}{@id})
}

Fix 'FATAL: Does not look like criticality is a CLASS field reference (xxxx) denoting a type one line xxx'

In Module_1,

	Criticality ::= ENUMERATED { reject, ignore, notify }

In Module_2,

	IMPORTS
		Criticality
	FROM Module_1

		someMessage SOME-CLASS ::= {
			CRITICALITY	ignore
		}

This pull request add the capability to resolve 'reject', 'ignore' and 'notify'
in Module_2.

The aforementioned error message displayed during processing the following ASN.1 excerpt.

S1AP-ELEMENTARY-PROCEDURES S1AP-ELEMENTARY-PROCEDURE ::= {
    S1AP-ELEMENTARY-PROCEDURES-CLASS-1 |
    S1AP-ELEMENTARY-PROCEDURES-CLASS-2,
    ...
}

S1AP-ELEMENTARY-PROCEDURES-CLASS-1 S1AP-ELEMENTARY-PROCEDURE ::= {
    handoverPreparation                |
...
    writeReplaceWarning,
    ...,
    uERadioCapabilityMatch             |
....
    uEContextResume
}

S1AP-ELEMENTARY-PROCEDURES-CLASS-2 S1AP-ELEMENTARY-PROCEDURE ::= {
    handoverNotification               |
...
    privateMessage,
    ...,
    downlinkUEAssociatedLPPaTransport  |
...
    mMECPRelocationIndication
}

Because S1AP-ELEMENTARY-PROCEDURES-CLASS-1 and S1AP-ELEMENTARY-PROCEDURES-CLASS-2
are resolved 'after' S1AP-ELEMENTARY-PROCEDURES, so the ioc tables of them are not
available during resolving S1AP-ELEMENTARY-PROCEDURES. So we can not drop the
latter's containedSubtype field at first pass of asn1f_resolve_constraints of fix
process.

We also add second pass of asn1f_resolve_constraints to have a chance to combine
ioc tables of S1AP-ELEMENTARY-PROCEDURES-CLASS-1 and
S1AP-ELEMENTARY-PROCEDURES-CLASS-2.