[wasm] Add a magic word and a version number to the binary.

src/wasm/wasm-module.h

Index: src/wasm/wasm-module.h
diff --git a/src/wasm/wasm-module.h b/src/wasm/wasm-module.h
index 90d0fcca820fa25f1129b14c54d262cb78c8e6e0..411b6e20d3a085c020a208c959c13b8c31543488 100644
--- a/src/wasm/wasm-module.h
+++ b/src/wasm/wasm-module.h
@@ -22,6 +22,8 @@ namespace wasm {
 const size_t kMaxModuleSize = 1024 * 1024 * 1024;
 const size_t kMaxFunctionSize = 128 * 1024;
 const size_t kMaxStringSize = 256;
+const uint32_t kWasmMagic = 0x6d736100;
+const uint32_t kWasmVersion = 0x0a;
 
 enum WasmSectionDeclCode {
   kDeclMemory = 0x00,