Support for C++ scoped enum class

There is currently no sane way to represent enum class in .pxd.

namespace lol {
enum class rofl : int {
    SOMETHING,
    MOAR = 1337
};

// at this point, accessible as rofl::MOAR
}
// here, accessible as lol::rofl::MOAR

A possible way of representing it would be:

cdef extern from "headername.h" namespace "lol":
    cdef enumclass rofl:
        SOMETHING
        MOAR

# accessed as
rofl.MOAR

Related: #1567

[kb-1000]

I think this workaround is also good:

cdef extern from "headername.h" namespace "lol":
    cdef enum rofl:
        SOMETHING "lol::rofl::SOMETHING",
        MOAR "lol::rofl::MOAR"

And then:

cdef void f(rofl arg)
    pass

f(rofl.SOMETHING)

[justinfx]

I had this same problem and came to the same workaround solution back in 2013: https://stackoverflow.com/a/15566540/496445

Someone brought this up to me today and I had a poke around to see if anything has improved around this since that time, but then I came across this ticket with the same workarounds.