WebAssembly 2.0新特性

Multiple values
- Function types allow more than one result.
  适配go语言等函数多返回值的特性。
- Block types can be arbitrary function types.
  控制块带参数，适配C语言等内联函数的展开。Wasm1.0里调用内联函数使用的是call指令。
Reference types
- Added funcref and externref as new value types and respective.
  表元素增加新类型。
  
  externref allows modules to hold references to objects provided by the host environment; in other words, you can pass a JavaScript object to your .wasm module. The .wasm module can’t really do much with the object via the type. What’s more important is that the module is holding a reference to a garbage collected object on the JavaScript heap. 持有外部引用，为将来wasm引入GC准备。参看Upcoming Features and Proposals
Bulk memory
- New memory instructions: memory.fill, memory.init, memory.copy, data.drop.
  对应C里的memcpy, memmove等，目的提高处理大块内存的性能。Wasm1.0里使用load, store指令操作内存，只能处理基本类型的数值。
Multiple table
coming soon