New format:
sysname: CYGWIN_NT-${osversion}-${os_build_number}[-WOW64]
nodename: `gethostname`
release: ${cygwin_version}-${API minor}.${arch}[.snap]
version: YYYY-MM-DD HH:MM UTC
machine: ${arch}
_GNU_SOURCE:
domainname: `getdomainname`
!_GNU_SOURCE:
__domainname: `getdomainname`
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>