Optionally derive formatting information from the input file.

With this patch, clang-format can analyze the input file for two
properties:
1. Is "int *a" or "int* a" more common.
2. Are non-C++03 constructs used, e.g. A<A<A>>.

With Google-style, clang-format will now use the more common style for
(1) and format C++03 compatible, unless it finds C++11 constructs in the
input.

llvm-svn: 174504