Support one-liner C++11 lambdas. (Closes #162)

Add new nl_cpp_lambda_leave_one_liners option to leave one-liner C++11
lambdas.
Support newline addition/removal before opening brace for C++11 lambda.

Add new nl_cpp_ldef_brace option to add/remove/force newline before C++11
lambda opening brace.
Update etc/defaults.cfg with missing options, from --update-config-with-doc.
Merge pull request #180 from berenm/cpp-lambdas

Better support for C++11 lambdas formatting.