jer: Fix NULL

JER decoder

Per Chetan Pandey, addressing missing include that leaves random() undeclared

As per #493 in vlm/asn1c by Chetan Pandey, fixing the timezone macro

Fixes mouse07410/asn1c#134

WITH SUCCESSORS/DESCENDANTS support

Fix indentation that bothers CI compiler

fix issue #126: decoding extensible CHOICE error

Disable ASN__STACK_OVERFLOW_CHECK if building with Asan enabled

    The constraints ct was not effective for extensible CHOICE, so if ct && ct->flags & APC_EXTENSIBLE was true,
    ct was set to 0. Using normal CHOICE constraint in decoding extensible CHOICE was weird.
    We should change the normal CHOICE constraint to extensible CHOICE constraint when decoding extensible CHOICE,
    the extensible CHOICE constraint was lb=0,ub=specs->tag2el_count-specs->ext_start-1. So the conditional structure
    should be if specs && specs->tag2el_count > specs->ext_start, then decoding the CHOICE which range
    was specs->tag2el_count - specs->ext_start, and add specs->ext_start to value in the last.

When JER was added it was based on XER, which has BASIC-XER and
CANONICAL-XER.
So originally we had BASIC-JER, which isn't a real thing.

This renames ATS_BASIC_JER to ATS_JER and adds JER in the list of
encodings in the readme.

For empty extensible SEQUENCE type, e.g.

  searchSpaceType              CHOICE {
    common                       SEQUENCE {
      dci-Format0-0-AndFormat1-0     SEQUENCE {
        ...
      }                                                           OPTIONAL,   -- Need R
      dci-Format2-0                SEQUENCE {
        nrofCandidates-SFI           SEQUENCE {
          aggregationLevel1            ENUMERATED {n1, n2}        OPTIONAL,   -- Need R
          aggregationLevel2            ENUMERATED {n1, n2}        OPTIONAL,   -- Need R
          aggregationLevel4            ENUMERATED {n1, n2}        OPTIONAL,   -- Need R
          aggregationLevel8            ENUMERATED {n1, n2}        OPTIONAL,   -- Need R
          aggregationLevel16           ENUMERATED {n1, n2}        OPTIONAL    -- Need R
        },
        ...
      }                                                         OPTIONAL,   -- Need R
      dci-Format2-1                SEQUENCE {
        ...
      }                                                         OPTIONAL,   -- Need R
      dci-Format2-2                SEQUENCE {
        ...
      }                                                         OPTIONAL,   -- Need R
      dci-Format2-3                SEQUENCE {
        dummy1                       ENUMERATED {sl1, sl2, sl4, sl5, sl8, sl10, sl16, sl20}    OPTIONAL,   -- Cond Setup
        dummy2                       ENUMERATED {n1, n2},
        ...
      }                                                         OPTIONAL    -- Need R
    },
    ue-Specific                    SEQUENCE {
      dci-Formats                    ENUMERATED {formats0-0-And-1-0, formats0-1-And-1-1},
      ...
    }
  }

According to X.691 :

  If the sequence type has an extension marker in the "ComponentTypeLists"
  or in the "SequenceType" productions, then a single bit shall first be added to
  the field-list in a bit-field of length one.

So for dci-Format0-0-AndFormat1-0, dci-Format2-1 and dci-Format2-2,
even they are empty without other fields, there shall be still one extension bit
to be added.

Use compute_extensions_start() to determine position of extension in
asn1c_lang_C_type_SEQUENCE_def() to fix this problem.

ProtocolExtensionField.c generated from the following excerpt from ASN.1 of F1AP v15.4.0 :

RRC-Version ::= SEQUENCE {
    latest-RRC-Version BIT STRING (SIZE(3)),
    iE-Extensions      ProtocolExtensionContainer { { RRC-Version-ExtIEs } } OPTIONAL}

RRC-Version-ExtIEs F1AP-PROTOCOL-EXTENSION ::= {
    {ID id-latest-RRC-Version-Enhanced CRITICALITY ignore EXTENSION OCTET STRING (SIZE(3)) PRESENCE optional },
    ...
}

failed to be compiled because asn_PER_memb_OCTET_STRING_SIZE_3__constr_31 is not generated.

The reason is constraints of types used in information object sets are not processed in asn1fix() stage
so it's constraint, i.e. (SIZE(3)) in this case, is not generated.

With this fix, OCTET STRING (SIZE(3)) used in ASN.1 of F1AP v15.4.0 can be correctly processed
and generated code can be compiled.

However, this fix does not work for all sorts of types.

For example, if information object refer to a type like this : SEQUENCE (SIZE(3)) OF INTEGER
it will be failed to compiled because asn_IOS_RRC_Version_ExtIEs_1_rows[] refers to non-existing
asn_DEF_SEQUENCE_OF.