Revert "Remove V8_HOST_CAN_READ_UNALIGNED and its uses."

src/regexp-macro-assembler.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_REGEXP_MACRO_ASSEMBLER_H_
 #define V8_REGEXP_MACRO_ASSEMBLER_H_
 
 #include "src/ast.h"
 
 namespace v8 {
@@ skipping 30 matching lines @@
     kNoStackLimitCheck = false,
     kCheckStackLimit = true
   };
 
   explicit RegExpMacroAssembler(Zone* zone);
   virtual ~RegExpMacroAssembler();
   // The maximal number of pushes between stack checks. Users must supply
   // kCheckStackLimit flag to push operations (instead of kNoStackLimitCheck)
   // at least once for every stack_limit() pushes that are executed.
   virtual int stack_limit_slack() = 0;
-  virtual bool CanReadUnaligned() = 0;
+  virtual bool CanReadUnaligned();
   virtual void AdvanceCurrentPosition(int by) = 0;  // Signed cp change.
   virtual void AdvanceRegister(int reg, int by) = 0;  // r[reg] += by.
   // Continues execution from the position pushed on the top of the backtrack
   // stack by an earlier PushBacktrack(Label*).
   virtual void Backtrack() = 0;
   virtual void Bind(Label* label) = 0;
   virtual void CheckAtStart(Label* on_at_start) = 0;
   // Dispatch after looking the current character up in a 2-bits-per-entry
   // map.  The destinations vector has up to 4 labels.
   virtual void CheckCharacter(unsigned c, Label* on_equal) = 0;
@@ skipping 167 matching lines @@
                         int* output,
                         int output_size,
                         Isolate* isolate);
 };
 
 #endif  // V8_INTERPRETED_REGEXP
 
 } }  // namespace v8::internal
 
 #endif  // V8_REGEXP_MACRO_ASSEMBLER_H_