Fix introspection building for Visual Studio builds

Fix introspection building for Visual Studio builds

Apparently time_t is used in gtkrecentmanager.h, which is a special type
that could not be recognized when Gtk-3.0.gir is built.  Judging from the
ast.py from the gobject-introspection package, we can define time_t as
long, and this will allow pygobject to load the Gtk module from
gi.repository.