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.

Tests/CTestTestFdSetSize/sleep.c

@@ -1,7 +1,7 @@
 #if defined(_WIN32)
-#include <windows.h>
+#  include <windows.h>
 #else
-#include <unistd.h>
+#  include <unistd.h>
 #endif
 
 /* sleeps for 0.1 second */