Move all the HAVE() macros related to string manipulations to wtf/StringExtras.h.

Source/wtf/StringExtras.h

 /*
  * Copyright (C) 2006, 2010 Apple 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:
  * 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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WTF_StringExtras_h
 #define WTF_StringExtras_h
 
+#if OS(UNIX)
+#define HAVE_STRINGS_H 1
+#endif
+
+#if !defined(HAVE_STRNSTR)
+#if OS(DARWIN) || (OS(FREEBSD) && !defined(__GLIBC__))
+#define HAVE_STRNSTR 1
+#endif
+#endif
+
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 
 #if HAVE(STRINGS_H)
 #include <strings.h>
 #endif
 
 #if COMPILER(MSVC)
 // FIXME: why a COMPILER check instead of OS? also, these should be HAVE checks
@@ skipping 52 matching lines @@
     for (const char* start = buffer; *start && start + targetLength <= buffer + bufferLength; start++) {
         if (*start == *target && strncmp(start + 1, target + 1, targetLength - 1) == 0)
             return const_cast<char*>(start);
     }
     return 0;
 }
 
 #endif
 
 #endif // WTF_StringExtras_h