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

internal/ceres/stringprintf.cc

diff --git a/internal/ceres/stringprintf.cc b/internal/ceres/stringprintf.cc
index d1e016a..c0f3522 100644
--- a/internal/ceres/stringprintf.cc
+++ b/internal/ceres/stringprintf.cc
@@ -39,8 +39,9 @@
 namespace ceres {
 namespace internal {
 
-#ifdef COMPILER_MSVC
+#ifdef _MSC_VER
 enum { IS_COMPILER_MSVC = 1 };
+#define va_copy(d,s) ((d) = (s))
 #else
 enum { IS_COMPILER_MSVC = 0 };
 #endif