C language improve and refactor

[phodal]

link to: https://github.com/archguard/archguard/issues/96

[phodal]

https://github.com/doxygen/doxygen/blob/master/src/classdef.cpp

For our strategy, simliar to Rust

• file as container
• structure as structure
• all other functions in default
• careful about pointer maybe take a look on clangparser.cpp

static QCString getCompoundTypeString(SrcLangExt lang,ClassDef::CompoundType compType,bool isJavaEnum)
{
  if (lang==SrcLangExt_Fortran)
  {
    switch (compType)
    {
      case ClassDef::Class:     return "module";
      case ClassDef::Struct:    return "type";
      case ClassDef::Union:     return "union";
      case ClassDef::Interface: return "interface";
      case ClassDef::Protocol:  return "protocol";
      case ClassDef::Category:  return "category";
      case ClassDef::Exception: return "exception";
      default:                  return "unknown";
    }
  }
  else
  {
    switch (compType)
    {
      case ClassDef::Class:     return isJavaEnum ? "enum" : "class";
      case ClassDef::Struct:    return "struct";
      case ClassDef::Union:     return "union";
      case ClassDef::Interface: return lang==SrcLangExt_ObjC ? "class" : "interface";
      case ClassDef::Protocol:  return "protocol";
      case ClassDef::Category:  return "category";
      case ClassDef::Exception: return "exception";
      case ClassDef::Service:   return "service";
      case ClassDef::Singleton: return "singleton";
      default:                  return "unknown";
    }
  }
}