Port Ceres to Windows

This is a preliminary, but full, port of Ceres to Windows.
Currently all tests compile and run, with only system_test
failing to work correctly due to a path issue.

Change-Id: I4152c1588bf51ffd7f4d9401ef9759f5d28c299c
diff --git a/internal/ceres/collections_port.h b/internal/ceres/collections_port.h
index 7255285..e125f3f 100644
--- a/internal/ceres/collections_port.h
+++ b/internal/ceres/collections_port.h
@@ -33,8 +33,13 @@
 #ifndef CERES_INTERNAL_COLLECTIONS_PORT_H_
 #define CERES_INTERNAL_COLLECTIONS_PORT_H_
 
+#if defined(_MSC_VER) && _MSC_VER <= 1600
+#include <unordered_map>
+#include <unordered_set>
+#else
 #include <tr1/unordered_map>
 #include <tr1/unordered_set>
+#endif
 #include <utility>
 #include "ceres/integral_types.h"
 #include "ceres/internal/port.h"