Generate C wrappers for functions that pass structs by value

[kornilova203]

Scala code will not compile if there are structs that are passed by value.
Example:

struct MyStruct {
    int a;
};

struct OtherStruct {
    struct MyStruct s;
};

This Scala code will not compile:

@native.link("Lib")
@native.extern
object Lib {
  type struct_MyStruct = native.CStruct1[native.CInt]
  type struct_OtherStruct = native.CStruct1[struct_MyStruct]
}

import Lib._

object LibMembersHelpers {
  implicit class struct_OtherStruct_ops(val p: native.Ptr[struct_OtherStruct]) extends AnyVal {
    def s: struct_MyStruct = !p._1 // error
    def s_=(value: struct_MyStruct):Unit = !p._1 = value // error
  }
}

One possible solution - remove declarations that use structs by value.
Another - generate C code that converts struct to a pointer