Log Message:
Changes 2.2.11:
* Fix comma operator in libsigc++ lambda expressions.
* Added SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE.
  This allows most uses of libsigc++'s lambda expressions to be
  replaced by standard C++11 lambda expressions.
* Use std::size_t and std::ptrdiff_t instead
* Fix 'make check' with gcc 4.7.
* Enable test_lambda in 'make check'.