if SOCK_NONBLOCK is defined, use it instead of socket+fcntl

CHANGES

@@ -26,6 +26,7 @@
   more constness for stralloc and buffer
   mmap_read/mmap_shared on zero length files no longer fail but return a
     zero length buffer
+  if SOCK_NONBLOCK is defined, use it instead of socket+fcntl
 
 0.29:
   save 8 bytes in taia.h for 64-bit systems

socket/socket_tcp4.c

@@ -1,10 +1,19 @@
+#include <sys/types.h>
+#ifndef __MINGW32__
 #include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#endif
 #include "socket.h"
 #include "ndelay.h"
 
 int socket_tcp4(void) {
+#ifdef SOCK_NONBLOCK
+  return socket(PF_INET,SOCK_STREAM|SOCK_NONBLOCK,IPPROTO_TCP);
+#else
   int s=socket_tcp4b();
   if (s==-1) return -1;
   if (ndelay_on(s) == -1) { close(s); return -1; }
   return s;
+#endif
 }

socket/socket_tcp6.c

@@ -1,10 +1,21 @@
+#include <sys/types.h>
+#ifndef __MINGW32__
 #include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#endif
+#include <errno.h>
+#include "haveip6.h"
 #include "socket.h"
 #include "ndelay.h"
 
 int socket_tcp6(void) {
+#if defined(LIBC_HAS_IP6) && defined(SOCK_NONBLOCK)
+  return socket(PF_INET6,SOCK_STREAM|SOCK_NONBLOCK,IPPROTO_TCP);
+#else
   int s=socket_tcp6b();
   if (s==-1) return -1;
   if (ndelay_on(s) == -1) { close(s); return -1; }
   return s;
+#endif
 }