Issue #2731 - Fix crashes on unknown BigInt types in JIT

This only works around the unknown type crashes but doesn't actually fix
attempts at using 64-bit BigInts in Ion.
Resolves #2731

js/src/jit/MacroAssembler.cpp

@@ -2124,6 +2124,7 @@ MacroAssembler::convertTypedOrValueToInt(TypedOrValueRegister src, FloatRegister
       case MIRType::String:
       case MIRType::Symbol:
       case MIRType::Object:
+      case MIRType::BigInt:
         jump(fail);
         break;
       default:

js/src/jit/MacroAssembler.h

@@ -1622,6 +1622,11 @@ class MacroAssembler : public MacroAssemblerSpecific
           case Scalar::Uint32:
             store32(value, dest);
             break;
+          case Scalar::BigInt64:
+          case Scalar::BigUint64:
+            //FIXME: storing 64-bit values doesn't actually work yet.
+            // store64(value, dest);
+            break;
           default:
             MOZ_CRASH("Invalid typed array type");
         }