This somewhat heavyweight solution will avoid size_t/long long/long/int
mismatches on various platforms once and for all. The previous template
overloads could e.g. not handle size_t on Darwin.
One gotcha: the 'format_descriptor<T>::value()' syntax changed to just
'format_descriptor<T>::value'
- new pybind11::base<> attribute to indicate a subclass relationship
- unified infrastructure for parsing variadic arguments in class_ and cpp_function
- use 'handle' and 'object' more consistently everywhere
The array(const buffer_info &info) constructor fails when given
complex types since their format string is 'Zd' or 'Zf' which has
a length of two and causes an error here:
if (info.format.size() != 1)
throw std::runtime_error("Unsupported buffer format!");
Fixed by allowing format sizes of one and two.
