Add the emitp function for X64 assembler

src/x64/assembler-x64.h

Index: src/x64/assembler-x64.h
===================================================================
--- src/x64/assembler-x64.h	(revision 15744)
+++ src/x64/assembler-x64.h	(working copy)
@@ -1443,8 +1443,8 @@
   void GrowBuffer();
 
   void emit(byte x) { *pc_++ = x; }
+  inline void emit(uintptr_t x, RelocInfo::Mode rmode);

[danno, 2013/07/23 12:40:54]

why not call this emitp (i.e. for "pointer") and have it take a void* parameter?
I think that makes it clearer. Then some of the reinterpret_cast nastiness can
be hidden and centralized inside emitp.

[haitao.feng, 2013/07/24 06:35:12]

Done.

   inline void emitl(uint32_t x);
-  inline void emitq(uint64_t x, RelocInfo::Mode rmode);

[danno, 2013/07/23 12:40:54]

I don't see a need to remove this. Please leave it in and just add a new
function.

[haitao.feng, 2013/07/24 06:35:12]

Done.

   inline void emitw(uint16_t x);
   inline void emit_code_target(Handle<Code> target,
                                RelocInfo::Mode rmode,