Revert "Delete and re-add libpqxx-7.7.3 due to weird corruption."

This reverts commit e96515433d.

ext/libpqxx-7.7.3/include/pqxx/internal/gates/connection-transaction.hxx

@@ -0,0 +1,44 @@
+#include <pqxx/internal/callgate.hxx>
+
+namespace pqxx
+{
+class connection;
+}
+
+namespace pqxx::internal::gate
+{
+class PQXX_PRIVATE connection_transaction : callgate<connection>
+{
+  friend class pqxx::transaction_base;
+
+  connection_transaction(reference x) : super(x) {}
+
+  template<typename STRING> result exec(STRING query, std::string_view desc)
+  {
+    return home().exec(query, desc);
+  }
+
+  void register_transaction(transaction_base *t)
+  {
+    home().register_transaction(t);
+  }
+  void unregister_transaction(transaction_base *t) noexcept
+  {
+    home().unregister_transaction(t);
+  }
+
+  auto read_copy_line() { return home().read_copy_line(); }
+  void write_copy_line(std::string_view line) { home().write_copy_line(line); }
+  void end_copy_write() { home().end_copy_write(); }
+
+  result exec_prepared(zview statement, internal::c_params const &args)
+  {
+    return home().exec_prepared(statement, args);
+  }
+
+  result exec_params(zview query, internal::c_params const &args)
+  {
+    return home().exec_params(query, args);
+  }
+};
+} // namespace pqxx::internal::gate