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/cmCPluginAPI.cxx

@@ -7,6 +7,8 @@
 
 #include "cmCPluginAPI.h"
 
+#include <cstdlib>
+
 #include "cmExecutionStatus.h"
 #include "cmGlobalGenerator.h"
 #include "cmMakefile.h"
@@ -14,8 +16,6 @@
 #include "cmState.h"
 #include "cmVersion.h"
 
-#include <cstdlib>
-
 #ifdef __QNX__
 #  include <malloc.h> /* for malloc/free on QNX */
 #endif