Add support for the "history" node on MUC join

Supports the "seconds", "maxstanzas", "since" and "maxchars" (but only =0)
attributes.

fix #3270

src/bridge/history_limit.hpp

@@ -0,0 +1,8 @@
+#pragma once
+
+// Default values means no limit
+struct HistoryLimit
+{
+  int stanzas{-1};
+  std::string since{};
+};