x86/x64 port of Math.floor(x/y) to use integer division for specific divisor

src/ia32/disasm-ia32.cc

Index: src/ia32/disasm-ia32.cc
===================================================================
--- src/ia32/disasm-ia32.cc	(revision 11554)
+++ src/ia32/disasm-ia32.cc	(working copy)
@@ -553,6 +553,7 @@
       case 2: mnem = "not"; break;
       case 3: mnem = "neg"; break;
       case 4: mnem = "mul"; break;
+      case 5: mnem = "imul"; break;
       case 7: mnem = "idiv"; break;
       default: UnimplementedInstruction();
     }
@@ -1663,7 +1664,8 @@
 
 int Disassembler::InstructionDecode(v8::internal::Vector<char> buffer,
                                     byte* instruction) {
-  DisassemblerIA32 d(converter_, false /*do not crash if unimplemented*/);
+///  DisassemblerIA32 d(converter_, false /*do not crash if unimplemented*/);
+  DisassemblerIA32 d(converter_, true /*do not crash if unimplemented*/);
   return d.InstructionDecode(buffer, instruction);
 }