netdb: also supply struct addrinfo for cygwin 1.5.x * m4/netdb_h.m4 (gl_HEADER_NETDB): Check for incomplete header on older cygwin. * lib/netdb.in.h [!HAVE_STRUCT_ADDRINFO]: Also supply contents for cygwin. * doc/posix-headers/netdb.texi (netdb.h): Document this. Signed-off-by: Eric Blake <ebb9@byu.net>