Become a little smarter with formatting long chains of pipes.

Assign a high penalty to breaking before "<<" if the previous token is a
string literal ending in ":" or "=".

Before:
llvm::outs()
    << "aaaaaaaaaaaaaaaaa = " << aaaaaaaaaaaaaaaaa << "bbbbbbbbbbbbbbbbb = "
    << bbbbbbbbbbbbbbbbb << "ccccccccccccccccc = " << ccccccccccccccccc
    << "ddddddddddddddddd = " << ddddddddddddddddd << "eeeeeeeeeeeeeeeee = "
    << eeeeeeeeeeeeeeeee;

After:
llvm::outs() << "aaaaaaaaaaaaaaaaa = " << aaaaaaaaaaaaaaaaa
             << "bbbbbbbbbbbbbbbbb = " << bbbbbbbbbbbbbbbbb
             << "ccccccccccccccccc = " << ccccccccccccccccc
             << "ddddddddddddddddd = " << ddddddddddddddddd
             << "eeeeeeeeeeeeeeeee = " << eeeeeeeeeeeeeeeee;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174545 91177308-0d34-0410-b5e6-96231b3b80d8