Add the emitp function for X64 assembler

src/x64/assembler-x64-inl.h

Index: src/x64/assembler-x64-inl.h
===================================================================
--- src/x64/assembler-x64-inl.h	(revision 15744)
+++ src/x64/assembler-x64-inl.h	(working copy)
@@ -45,21 +45,21 @@
 static const byte kCallOpcode = 0xE8;
 
 
+void Assembler::emit(uintptr_t x, RelocInfo::Mode rmode) {
+  Memory::uintptr_at(pc_) = x;
+  if (!RelocInfo::IsNone(rmode)) {
+    RecordRelocInfo(rmode, x);
+  }
+  pc_ += sizeof(uintptr_t);
+}
+
+
 void Assembler::emitl(uint32_t x) {
   Memory::uint32_at(pc_) = x;
   pc_ += sizeof(uint32_t);
 }
 
 
-void Assembler::emitq(uint64_t x, RelocInfo::Mode rmode) {
-  Memory::uint64_at(pc_) = x;
-  if (!RelocInfo::IsNone(rmode)) {
-    RecordRelocInfo(rmode, x);
-  }
-  pc_ += sizeof(uint64_t);
-}
-
-
 void Assembler::emitw(uint16_t x) {
   Memory::uint16_at(pc_) = x;
   pc_ += sizeof(uint16_t);