Crash when reserved keywords are used in 3d

[Smfakhoury]

Everparse crashes when encountering 3d code that uses reserved keywords as identifier names.

Sample 3d code using 'type' identifier:

typedef UINT32BE START;

typedef struct _REPLY{
    UINT32BE requestor_id;
    UINT32BE response_id;
} REPLY;

typedef struct _CLOSE{
    UINT32BE requestor_id;
    UINT32BE response_id;
} CLOSE;

casetype _PAYLOAD(UINT8 type){
    switch(type){
        case 0: START message;
        case 1: REPLY message;
        case 2: CLOSE message;
    }
} PAYLOAD;

entrypoint 
typedef struct _MESSAGES{
    UINT8 type {type == 0 || type == 1 || type == 2};
    UINT32BE length;
    PAYLOAD(type) messages[:byte-size length];

} MESSAGES;

Crashes with the following:

Processing files: ./examples/Sample.3d
Writing file ./Sample.fst
Writing file ./Sample.fsti
Writing file ./SampleWrapper.c
Writing file ./SampleWrapper.h
Running: /home/sfakhoury/everparse/everparse/bin/fstar.exe --print_in_place --odir . --cache_dir . --include /home/sfakhoury/everparse/everparse/src/3d/prelude/buffer --include . --already_cached Prims,LowStar,FStar,LowParse,C,EverParse3d.\*,Spec --include /home/sfakhoury/everparse/everparse/src/lowparse --include /home/sfakhoury/everparse/everparse/krmllib --include /home/sfakhoury/everparse/everparse/krmllib/obj --include /home/sfakhoury/everparse/everparse/src/3d/prelude --cmi --warn_error +241 ./Sample.fsti
Running: /home/sfakhoury/everparse/everparse/bin/fstar.exe --print_in_place --odir . --cache_dir . --include /home/sfakhoury/everparse/everparse/src/3d/prelude/buffer --include . --already_cached Prims,LowStar,FStar,LowParse,C,EverParse3d.\*,Spec --include /home/sfakhoury/everparse/everparse/src/lowparse --include /home/sfakhoury/everparse/everparse/krmllib --include /home/sfakhoury/everparse/everparse/krmllib/obj --include /home/sfakhoury/everparse/everparse/src/3d/prelude --cmi --warn_error +241 ./Sample.fst
* Error 168 at ./Sample.fst(166,22-166,22):
  - Syntax error

1 error was reported (see above)

exit 1

Line 166 in Sample.fst:

let def__PAYLOAD (type:(___UINT8 )) = ( (T_cases (type = 0uy) (T_with_comment "message" (T_denoted "message" (DT_IType UInt32BE)) "Validating field message") (T_cases (type = 1uy) (T_with_comment "message" (T_denoted "message" (dtyp__REPLY )) "Validating field message") (T_cases (type = 2uy) (T_with_comment "message" (T_denoted "message" (dtyp__CLOSE )) "Validating field message") (T_false "_x_0")))) <: Tot (typ _ _ _ _) by (T.norm [delta_attr [`%specialize]; zeta; iota; primops]; T.smt()))