Randomly placed definition of S_ISDIR() in psql/copy.c

Why does psql/copy.c contain this?

#if defined(WIN32) && !defined(S_ISDIR)
#define __S_ISTYPE(mode, mask)    (((mode) & S_IFMT) == (mask))
#define S_ISDIR(mode)     __S_ISTYPE((mode), S_IFDIR)
#endif

Surely a better place for such a thing is src/include/port/win32.h
... where indeed there already is a definition of S_ISDIR().
So I think this is dead code as well as poor style.  Any objection to
seeing what happens if we remove it?
        regards, tom lane