devel/cdecl: update to 6.4.

Added support for user-defined conversion operators
Now supports C++ user-defined conversion operators.

cdecl> explain operator int const*() const
declare constant user-defined conversion operator returning pointer to constant int
Added support for alignment specifiers
Now supports C11 _Alignas and C++11 alignas specifiers.

cdecl> explain _Alignas(64) int x
declare x as int aligned as 16 bytes
Added more predefined typedefs
More predefined typedefs were added: fd_set, nfds_t, and sigset_t.

Reported by: portscout