Introduce InvokeMathCFunction that can be used to directly invoke mathematical function provided by…

runtime/vm/disassembler_x64.cc

Index: runtime/vm/disassembler_x64.cc
diff --git a/runtime/vm/disassembler_x64.cc b/runtime/vm/disassembler_x64.cc
index f8ab7be9834f907c67cfaf21ec44a047efcbd300..4d150720a75f36f7e92f5855e4dd22802036fc7c 100644
--- a/runtime/vm/disassembler_x64.cc
+++ b/runtime/vm/disassembler_x64.cc
@@ -1509,6 +1509,13 @@ int DisassemblerX64::InstructionDecode(uword pc) {
         data += 3;
         break;
 
+      case 0xC8:
+        AppendToBuffer("enter %d, %d",
+                       *reinterpret_cast<uint16_t*>(data + 1),
+                       data[3]);
+        data += 4;
+        break;
+
       case 0x69:  // fall through
       case 0x6B: {
         int mod, regop, rm;