Change for systems with >1 ways of setting (non-)blocking

mode. (djgpp/Watt-32 has 3 ways). Should rewrite this using
"#elif ..", but maybe there is still broken cpp around?

lib/connect.c

@@ -133,6 +133,7 @@ int Curl_nonblock(curl_socket_t sockfd,    /* operate on this */
                   int nonblock   /* TRUE or FALSE */)
 {
 #undef SETBLOCK
+#define SETBLOCK 0
 #ifdef HAVE_O_NONBLOCK
   /* most recent unix versions */
   int flags;
@@ -145,43 +146,48 @@ int Curl_nonblock(curl_socket_t sockfd,    /* operate on this */
 #define SETBLOCK 1
 #endif
 
-#ifdef HAVE_FIONBIO
+#if defined(HAVE_FIONBIO) && (SETBLOCK == 0)
   /* older unix versions */
   int flags;
 
   flags = nonblock;
   return ioctl(sockfd, FIONBIO, &flags);
+#undef SETBLOCK
 #define SETBLOCK 2
 #endif
 
-#ifdef HAVE_IOCTLSOCKET
+#if defined(HAVE_IOCTLSOCKET) && (SETBLOCK == 0)
   /* Windows? */
   unsigned long flags;
   flags = nonblock;
 
   return ioctlsocket(sockfd, FIONBIO, &flags);
+#undef SETBLOCK
 #define SETBLOCK 3
 #endif
 
-#ifdef HAVE_IOCTLSOCKET_CASE
+#if defined(HAVE_IOCTLSOCKET_CASE) && (SETBLOCK == 0)
   /* presumably for Amiga */
   return IoctlSocket(sockfd, FIONBIO, (long)nonblock);
+#undef SETBLOCK
 #define SETBLOCK 4
 #endif
 
-#ifdef HAVE_SO_NONBLOCK
+#if defined(HAVE_SO_NONBLOCK) && (SETBLOCK == 0)
   /* BeOS */
   long b = nonblock ? 1 : 0;
   return setsockopt(sockfd, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b));
+#undef SETBLOCK
 #define SETBLOCK 5
 #endif
 
 #ifdef HAVE_DISABLED_NONBLOCKING
   return 0; /* returns success */
+#undef SETBLOCK
 #define SETBLOCK 6
 #endif
 
-#ifndef SETBLOCK
+#if (SETBLOCK == 0)
 #error "no non-blocking method was found/used/set"
 #endif
 }