Don't insert confusing line breaks in comparisons.

In general, clang-format breaks after an operator if the LHS spans
multiple lines. Otherwise, this can lead to confusing effects and
effectively hide the operator precendence, e.g. in

if (aaaaaaaaaaaaaa ==
        bbbbbbbbbbbbbb && c) { ...

This patch removes this rule for comparisons, if the LHS is not a binary
expression itself as many users were wondering why clang-format inserts
an unnecessary linebreak.

Before:
if (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) >
    5) { ...

After:
if (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) > 5) { ...

In the long run, we might:
- Want to do this for other binary expressions as well.
- Do this only if the RHS is short or even only if it is a literal.

llvm-svn: 185530