Fix Windows strerror_r() implementation

Commit 6351586a771e9a99e1e946cc9a0b6a87bbb14094 (ticket 7961)
introduced several variants of strerror_r().  The Windows one
contained a bug which made its return value undefined; fix that.

https://github.com/krb5/krb5/commit/e952578cab6c954c3804323fb5ff256858c3b86c
Author: Greg Hudson <ghudson@mit.edu>
Commit: e952578cab6c954c3804323fb5ff256858c3b86c
Branch: master
 src/util/support/strerror_r.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)