Revise include order using clang-format-6.0

Run the `clang-format.bash` script to update our C and C++ code to a new
include order `.clang-format`.  Use `clang-format` version 6.0.

Source/cmFileMonitor.cxx

@@ -2,14 +2,15 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmFileMonitor.h"
 
-#include "cmAlgorithms.h"
-#include "cmsys/SystemTools.hxx"
-
 #include <cassert>
 #include <cstddef>
 #include <unordered_map>
 #include <utility>
 
+#include "cmsys/SystemTools.hxx"
+
+#include "cmAlgorithms.h"
+
 namespace {
 void on_directory_change(uv_fs_event_t* handle, const char* filename,
                          int events, int status);