Rename OS(UNIX) to OS(POSIX)

Source/wtf/RandomNumberSeed.h

 /*
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 16 matching lines @@
 #define WTF_RandomNumberSeed_h
 
 #include "RandomNumber.h"
 #include <stdlib.h>
 #include <time.h>
 
 #if HAVE(SYS_TIME_H)
 #include <sys/time.h>
 #endif
 
-#if OS(UNIX)
+#if OS(POSIX)
 #include <sys/types.h>
 #include <unistd.h>
 #endif
 
 namespace WTF {
 
 inline void initializeRandomNumberGenerator()
 {
 #if OS(MACOSX)
     // On Darwin we use arc4random which initialises itself.
 #elif COMPILER(MSVC) && defined(_CRT_RAND_S)
     // On Windows we use rand_s which initialises itself
-#elif OS(UNIX)
+#elif OS(POSIX)
     // srandomdev is not guaranteed to exist on linux so we use this poor seed, this should be improved
     timeval time;
     gettimeofday(&time, 0);
     srandom(static_cast<unsigned>(time.tv_usec * getpid()));
 #else
     srand(static_cast<unsigned>(time(0)));
 #endif
 
 }
 
 }
 
 #endif