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.

Tests/LoadCommandOneConfig/CMakeCommands/cmTestCommand.c

@@ -1,8 +1,9 @@
-#include "cmCPluginAPI.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "cmCPluginAPI.h"
+
 typedef struct
 {
   char* LibraryName;