Use high-resolution timer on Windows

This fixes a Windows specific issue where the
problem-summary reports timings as zero, as long as
the time difference in question is smaller than one
second.

Change-Id: Ibd91874294423af6acda2575eae80f01aabed6d3

internal/ceres/wall_time.cc

diff --git a/internal/ceres/wall_time.cc b/internal/ceres/wall_time.cc
index c353973..09e3c4a 100644
--- a/internal/ceres/wall_time.cc
+++ b/internal/ceres/wall_time.cc
@@ -50,7 +50,12 @@
   return omp_get_wtime();
 #else
 #ifdef _WIN32
-  return static_cast<double>(std::time(NULL));
+  LARGE_INTEGER count;
+  LARGE_INTEGER frequency;
+  QueryPerformanceCounter(&count);
+  QueryPerformanceFrequency(&frequency);
+  return static_cast<double>(count.QuadPart) /
+         static_cast<double>(frequency.QuadPart);
 #else
   timeval time_val;
   gettimeofday(&time_val, NULL);