clang-format: Be more conservative about specially indenting blocks in C++.

This is a bit of a step back of what we did in r222531, as there are
some corner cases in C++, where this kind of formatting is really bad.

Example:
Before:
  virtual aaaaaaaaaaaaaaaa(std::function<bool()> IsKindWeWant = [&]() {
    return true;
  }, aaaaa aaaaaaaaa);

After:
  virtual aaaaaaaaaaaaaaaa(std::function<bool()> IsKindWeWant =
                               [&]() { return true; },
                           aaaaa aaaaaaaaa);

The block formatting logic in JavaScript will probably go some other changes,
too, and we'll potentially be able to make the rules more consistent again. For
now, this seems to be the best approach for C++.

llvm-svn: 245694