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/cmFilePathChecksum.cxx

@@ -2,13 +2,13 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmFilePathChecksum.h"
 
+#include <vector>
+
 #include "cmBase32.h"
 #include "cmCryptoHash.h"
 #include "cmMakefile.h"
 #include "cmSystemTools.h"
 
-#include <vector>
-
 cmFilePathChecksum::cmFilePathChecksum() = default;
 
 cmFilePathChecksum::cmFilePathChecksum(std::string const& currentSrcDir,