Extensions surrounded by root components encoded incorrectly in BER

[vlm]

See https://sourceforge.net/projects/asn1c/forums/forum/357921/topic/5450713:

• 8.1.1.4: “NOTE: [...] all extensibility markers in CHOICE, SEQUENCE and SET are ignored, with the extensions treated as if they were in the extension root of the type”
• 8.9.2: “The contents octets shall consist of the complete encoding of one data value from each of the types listed in the ASN.1 definition of the sequence type, in the order of their appearance in the definition [...]”

[counselour]

I tried hacking around this by turning off the root and extension splitting in asn1fix_constr.c, but the code in constr_SEQUENCE.c where IN_EXTENSION_GROUP is used seems to really rely on the extensions being at the end. And, there is code in the compiler that marks everything after the first extension marker as optional. I got a few things working but the big gprs and timon data flummoxed me. So, I have to undo the hack.

If you think you have a way to fix this, let me know what needs to be done. I can certainly try to implement a solution.