[wasm] Remove some small TODOs and small fixes.

src/wasm/wasm-opcodes.cc

Index: src/wasm/wasm-opcodes.cc
diff --git a/src/wasm/wasm-opcodes.cc b/src/wasm/wasm-opcodes.cc
index ba336b40365a13eb6adbde7f19967ca1ae7db75e..2110ad3aa9b7c8d810dfafb2488ba47f51dfae02 100644
--- a/src/wasm/wasm-opcodes.cc
+++ b/src/wasm/wasm-opcodes.cc
@@ -399,13 +399,6 @@ FunctionSig* WasmOpcodes::AtomicSignature(WasmOpcode opcode) {
       kSimpleExprSigs[kAtomicExprSigTable[opcode & 0xff]]);
 }
 
-// TODO(titzer): pull WASM_64 up to a common header.
-#if !V8_TARGET_ARCH_32_BIT || V8_TARGET_ARCH_X64
-#define WASM_64 1
-#else
-#define WASM_64 0
-#endif
-
 int WasmOpcodes::TrapReasonToMessageId(TrapReason reason) {
   switch (reason) {
 #define TRAPREASON_TO_MESSAGE(name) \