Make HAVE_MADV_FREE, HAVE_MADV_FREE_REUSE and HAVE_VIRTUALALLOC local macros as it only used in wtf…

Source/wtf/TCSystemAlloc.h

 // Copyright (c) 2005, 2007, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 46 matching lines @@
 // Pages which are released in this way may be destroyed (zeroed) by
 // the OS.  The benefit of this function is that it frees memory for
 // use by the system, the cost is that the pages are faulted back into
 // the address space next time they are touched, which can impact
 // performance.  (Only pages fully covered by the memory region will
 // be released, partial pages will not.)
 extern void TCMalloc_SystemRelease(void* start, size_t length);
 
 extern void TCMalloc_SystemCommit(void* start, size_t length);
 
-#if !HAVE(MADV_FREE_REUSE) && !HAVE(MADV_DONTNEED) && !HAVE(MMAP) && !HAVE(VIRTUALALLOC)
+#if OS(DARWIN)
+#define HAVE_MADV_FREE 1
+#define HAVE_MADV_FREE_REUSE 1
+#endif
+
+#if !HAVE(MADV_FREE_REUSE) && !HAVE(MADV_DONTNEED) && !HAVE(MMAP)
 inline void TCMalloc_SystemRelease(void*, size_t) { }
 #endif
 
-#if !HAVE(VIRTUALALLOC) && !HAVE(MADV_FREE_REUSE)
+#if !HAVE(MADV_FREE_REUSE)
 inline void TCMalloc_SystemCommit(void*, size_t) { }
 #endif
 
 #endif /* TCMALLOC_SYSTEM_ALLOC_H__ */