Add the emitp function for X64 assembler

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
===================================================================
--- src/x64/assembler-x64.cc	(revision 15840)
+++ src/x64/assembler-x64.cc	(working copy)
@@ -1377,7 +1377,7 @@
   EnsureSpace ensure_space(this);
   emit(0x48);  // REX.W
   emit(0xA1);
-  emitq(reinterpret_cast<uintptr_t>(value), mode);
+  emitp(value, mode);
 }
 
 
@@ -1529,7 +1529,7 @@
   EnsureSpace ensure_space(this);
   emit_rex_64(dst);
   emit(0xB8 | dst.low_bits());
-  emitq(reinterpret_cast<uintptr_t>(value), rmode);
+  emitp(value, rmode);
 }
 
 
@@ -1606,7 +1606,7 @@
     ASSERT(!HEAP->InNewSpace(*value));
     emit_rex_64(dst);
     emit(0xB8 | dst.low_bits());
-    emitq(reinterpret_cast<uintptr_t>(value.location()), mode);
+    emitp(value.location(), mode);
   }
 }
 
@@ -1998,7 +1998,7 @@
   EnsureSpace ensure_space(this);
   emit(0x48);  // REX.W
   emit(0xA3);
-  emitq(reinterpret_cast<uintptr_t>(dst), mode);
+  emitp(dst, mode);
 }