Initial support for formatting range-based for-loops.

Before (in good cases):
for (auto aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     : aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) {}
for (auto aaaaaaaaaaaaaaaaaaaa : aaaaaaaaaaaaaaaaaaaa(aaaaaaaaaaaaaaaaaaaa,
aaaa)) {}

After:
for (auto aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa :
     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa) {}
for (auto aaaaaaaaaaaaaaaaaaaa :
     aaaaaaaaaaaaaaaaaaaa(aaaaaaaaaaaaaaaaaaaa, aaaa)) {}

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173684 91177308-0d34-0410-b5e6-96231b3b80d8