struct support

[vincenthz]

• add support for lispy struct
• add support for rusty struct
• fix issue on the compilation/exec side if any

[vincenthz]

expected syntax:

Lispy:

(struct name (field1 field2 ... fieldN))

rusty:

struct name {
   field1,
   field2,
   ...
}

[vincenthz]

also need get/set accessor syntax, and constructor of value

(WIP syntax)

rust:

// constructor
record_name { field1: value1, field2: value2 ... }

// set
record_value.field = new_value

// get:
record_value.field

lisp:

; constructor
TBD

; set
(setf record_value field1 new_value_of_field)

; get
(getf record_value field1)