Remove unnecessary includes of v8 headers from platform files

src/platform.h

 // Copyright 2012 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 87 matching lines @@
 
 double modulo(double x, double y);
 
 // Custom implementation of math functions.
 double fast_exp(double input);
 double fast_sqrt(double input);
 // The custom exp implementation needs 16KB of lookup data; initialize it
 // on demand.
 void lazily_initialize_fast_exp();
 
+
 // ----------------------------------------------------------------------------
 // Fast TLS support
 
 #ifndef V8_NO_FAST_TLS
 
 #if defined(_MSC_VER) && V8_HOST_ARCH_IA32
 
 #define V8_FAST_TLS_SUPPORTED 1
 
 INLINE(intptr_t InternalGetExistingThreadLocal(intptr_t index));
@@ skipping 499 matching lines @@
   char name_[kMaxThreadNameLength];
   int stack_size_;
   Semaphore* start_semaphore_;
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_