[PowerPC] Add VSX builtins for vec_div

This patch adds builtin support for xvdivdp and xvdivsp, along with a
new test case.  The builtins are accessed using vec_div in altivec.h.
Builtins are listed (mostly) alphabetically there, so inserting these
changed the line numbers for deprecation warnings tested in
test/Headers/altivec-intrin.c.

There is a companion patch for LLVM.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221984 91177308-0d34-0410-b5e6-96231b3b80d8
clang-format: Improve indentation of comments in expressions.

Before:
  int i = (a)
              // comment
          + b;
  return aaaa == bbbb
                 // comment
             ? aaaa
             : bbbb;
After:
  int i = (a)
          // comment
          + b;
  return aaaa == bbbb
             // comment
             ? aaaa
             : bbbb;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221985 91177308-0d34-0410-b5e6-96231b3b80d8