Cygwin: uname: Raise size of utsname fields and revamp uname(2) output

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>

winsup/doc/new-features.xml

@@ -91,6 +91,10 @@ Remove matherr, and SVID and X/Open math library configurations.
 Default math library configuration is now IEEE.
 <listitem><para>
 
+</para></listitem>
+Improve uname(2) for newly built applications.
+</para></listitem>
+
 </itemizedlist>
 
 </sect2>