Revise C++ coding style using clang-format-6.0

Run the `clang-format.bash` script to update all our C and C++ code to a
new style defined by `.clang-format`.  Use `clang-format` version 6.0.

* If you reached this commit for a line in `git blame`, re-run the blame
  operation starting at the parent of this commit to see older history
  for the content.

* See the parent commit for instructions to rebase a change across this
  style transition commit.

Source/cmExportTryCompileFileGenerator.h

@@ -26,6 +26,7 @@ public:
 
   /** Set the list of targets to export.  */
   void SetConfig(const std::string& config) { this->Config = config; }
+
 protected:
   // Implement virtual methods from the superclass.
   bool GenerateMainFile(std::ostream& os) override;