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/cmCommonTargetGenerator.cxx

@@ -149,7 +149,8 @@ std::vector<std::string> cmCommonTargetGenerator::GetLinkedTargetDirectories()
     cmComputeLinkInformation::ItemVector const& items = cli->GetItems();
     for (auto const& item : items) {
       cmGeneratorTarget const* linkee = item.Target;
-      if (linkee && !linkee->IsImported()
+      if (linkee &&
+          !linkee->IsImported()
           // We can ignore the INTERFACE_LIBRARY items because
           // Target->GetLinkInformation already processed their
           // link interface and they don't have any output themselves.