stat() vs cygwin

It seems my fix for stat() broke cygwin, because it doesn't have
dosmaperr() available. The way I see it there are two ways to fix this:

1) Don't apply the stat fix for cygwin.

2) Make our dosmaperr() function be used on cygwin.

I don't know if the fix is actually needed on cygwin. Can someone with
access to such an environment test it and see?

The easy check, easier than the table, goes something along the line
of:
CREATE TABLE test(t int);
INSERT INTO test(t) SELECT * FROM generate_series(1,100000);
SELECT pg_relation_size('t');
SELECT pg_sleep(5);
SELECT pg_relation_size('t');

Without the patch on win32, the first pg_relation_size comes out as 0,
and the second one correct. With the patch, they come out equal. They
should, of course, always come out equal.

//Magnus