Fix Bug In Struct Field Initialization

Fields were not given default values when a struct was declared
without initializers.

Also, cleanup code in the helper function for binary operations
on struct instances.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/P4Compiler/Declarations.swift

@@ -106,7 +106,6 @@ struct StructDeclaration {
 
     if currentChild!.nodeType == "struct_declaration_fields" {
       currentChild!.enumerateNamedChildren { declaration_field in
-        print("declaration field: \(declaration_field)")
         switch VariableDeclarationStatement.Compile(
           node: declaration_field, withContext: current_context)
         {