* mklink2.cc (mkcygsymlink_nt): Allow 4K chars in symlink. Use strncat

	* mklink2.cc (mkcygsymlink_nt): Allow 4K chars in symlink.  Use strncat
	rather than strcat.
	* postinstall.cc (do_postinstall): Reset user token to original
	primary group.
	* win32.cc (NTSecurity::resetPrimaryGroup): New methid.
	(NTSecurity::setDefaultSecurity): Store original primary group in
	new NTSecurity member primaryGroupSID.  Set primary group in user token
	to Administrators group for admin users.  Align comment.
	* win32.h (class NTSecurity): Add member primaryGroupSID.
	(NTSecurity::resetPrimaryGroup): Declare.