system headers have two declarations for wchar_t, with different guard macros.
Not sure whether this is a bugfix candidate, that depends on what changed in the
curses module.
STRICT_SYSV_CURSES when compiling curses module on HP/UX. Generalize
access to _flags on systems where WINDOW is opaque. Fixes bugs
#432497, #422265, and the curses parts of #467145 and #473150.