Message 294071 - Python tracker

Hi, I finished various things and tackle the issue again, I opened PR 1689 at last.

Changes from previous patch:
* If ncurses doesn't have both is_pad function and _flags field of WINDOW, NCURSES_OPAQUE is defined as zero to make WINDOW to non-opaque type before including ncurses.h.
* The conditional compile on function definition are kept, it replaces WINDOW_HAS_FLAGS with py_is_pad macro itself.
* Unindent the blocks that places after section of the conditional compile on function definition.