printf("%.0f", 0.5) and round-to-even

[Eric Blake]

An interesting question popped up on the bug-gnu-utils list:
http://lists.gnu.org/archive/html/bug-gnu-utils/2008-09/msg00055.html

POSIX states that with %f, the low-order digit is rounded in an implementation-
defined manner.  However, since 0.5 is exactly half-way between 0 and 1, and 
most machines default to IEEE round-to-even, should we make the gnulib printf-
posix check enforce that printf("%.0f", 0.5) outputs "0" per round-to-even 
rules?  If so, then at least cygwin 1.5.x fails this check, by outputting "1".

-- 
Eric Blake