Check that types passed to PHYSFS_read are POD

More is needed to trap some misuses, but those traps flag existing code.
Use array<> for MarkerMessage
Enable using count_array_t<T,S> with prohibit_void_ptr<T>
Use array<> for Point_segs
Optimize multi_send_drop_marker
Use std::vector for lrgb_list
Unify dumpmine tmap loop
Add operator bool to exact_type<T>
Simplify lengthof header
Remove _may_repeat on check_cxx_works

self.__automatic_compiler_tests prevents repetition.