liteclient signature check support

1. update liteclient/liteserver. Now liteserver sends signatures of
blocks and liteclient checks them. I.e. liteclient completely checks
received data.
2. validator-engine: more GC options
3. blockchain-explorer: show all block transactions (instead of 256)
4. some bugfixes

tdutils/td/utils/port/StdStreams.cpp

@@ -27,6 +27,7 @@
 #include "td/utils/Slice.h"
 
 #include <atomic>
+#include <cassert>
 
 namespace td {
 
@@ -35,6 +36,7 @@ template <int id>
 static FileFd &get_file_fd() {
   static FileFd result = FileFd::from_native_fd(NativeFd(id, true));
   static auto guard = td::ScopeExit() + [&] { result.move_as_native_fd().release(); };
+  assert(!result.empty());
   return result;
 }
 

tdutils/td/utils/port/signals.cpp

@@ -329,6 +329,9 @@ static void default_failure_signal_handler(int sig) {
 }
 
 Status set_default_failure_signal_handler() {
+#if TD_PORT_POSIX
+  Stdin();  // init static variables before atexit
+#endif
   std::atexit(block_stdin);
   TRY_STATUS(setup_signals_alt_stack());
   TRY_STATUS(set_signal_handler(SignalType::Abort, default_failure_signal_handler));