stats: Fix swig wrapping for Tick in stats

Tick was not correctly wrapped for the stats system, and therefore it was not
possible to configure the stats dumping from the python scripts without
defining Ticks as long long. This patch fixes the wrapping of Tick by copying
the typemap of uint64_t to Tick.

src/python/swig/stats.i

@@ -123,6 +123,7 @@ reset()
 %ignore Stats::Info::flags;
 
 %import  "base/stats/types.hh"
+%import  "base/types.hh"
 
 %include "base/stats/info.hh"
 %include "base/stats/output.hh"
@@ -152,7 +153,7 @@ Output *initText(const std::string &filename, bool desc);
 void schedStatEvent(bool dump, bool reset,
                     Tick when = curTick(), Tick repeat = 0);
 
-void periodicStatDump(long long period = 0);
+void periodicStatDump(Tick period = 0);
 
 void updateEvents();