message: Set RetainCommentsFromSystemHeaders to true
  Note with -fretain-comments-from-system-headers, the .gch of bits/stdc++.h becomes larger by 1%, but that is fine.
  And improve comment handling in textDocument/hover
  Fix
diff: @@ -48,8 +48,11 @@ GetHover(DB *db, LanguageId lang, SymbolRef sym, int file_id) {
  std::optional<MarkedString> ls_comments, hover;
  WithEntity(db, sym, [&](const auto &entity) {
  for (auto &d : entity.def) {
  + if (!comments && d.comments[0])
  + comments = d.comments;
  if (d.spell) {
  - comments = d.comments[0] ? d.comments : nullptr;
  + if (d.comments[0])
  + comments = d.comments;
  if (const char *s =
  d.hover[0] ? d.hover
  : d.detailed_name[0] ? d.detailed_name : nullptr) {
  @@ -64,8 +67,6 @@ GetHover(DB *db, LanguageId lang, SymbolRef sym, int file_id) {
  }
  if (!hover && entity.def.size()) {
  auto &d = entity.def[0];
  - if (d.comments[0])
  - comments = d.comments;
  hover = {LanguageIdentifier(lang)};
  if (d.hover[0])
  hover->value = d.hover;
  