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

examples/powell.cc

@@ -45,8 +45,9 @@
 // Vol 7(1), March 1981.
 
 #include <vector>
-
 #include "ceres/ceres.h"
+#include "gflags/gflags.h"
+#include "glog/logging.h"
 
 using ceres::AutoDiffCostFunction;
 using ceres::CostFunction;