Add missing x86 imul opcode to disassembler

When playing with ART, I noticed that an integer multiply didn't
disassemble properly.  This patch adds the instruction.

Change-Id: Ic4d4921b1b301a9d674a257f094e8b3d834ed991
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>
diff --git a/disassembler/disassembler_x86.cc b/disassembler/disassembler_x86.cc
index 8781c7a..4a08ce0 100644
--- a/disassembler/disassembler_x86.cc
+++ b/disassembler/disassembler_x86.cc
@@ -515,6 +515,7 @@
           no_ops = true;
         }
         break;
+      case 0xAF: opcode << "imul"; has_modrm = true; load = true; break;
       case 0xB1: opcode << "cmpxchg"; has_modrm = true; store = true; break;
       case 0xB6: opcode << "movzxb"; has_modrm = true; load = true; break;
       case 0xB7: opcode << "movzxw"; has_modrm = true; load = true; break;