[wasm] Add support for import section.

src/wasm/wasm-opcodes.h

Index: src/wasm/wasm-opcodes.h
diff --git a/src/wasm/wasm-opcodes.h b/src/wasm/wasm-opcodes.h
index 88fb49afe18744a0c1d35e0fa548126117a4cb21..7cb9c00449c7f301424be47589e9177ed69c18af 100644
--- a/src/wasm/wasm-opcodes.h
+++ b/src/wasm/wasm-opcodes.h
@@ -68,6 +68,8 @@ struct MemoryAccess {
 typedef Signature<LocalType> FunctionSig;
 std::ostream& operator<<(std::ostream& os, const FunctionSig& function);
 
+// TODO(titzer): Renumber all the opcodes to fill in holes.
+
 // Control expressions and blocks.
 #define FOREACH_CONTROL_OPCODE(V) \
   V(Nop, 0x00, _)                 \
@@ -81,7 +83,6 @@ std::ostream& operator<<(std::ostream& os, const FunctionSig& function);
   V(TableSwitch, 0x08, _)         \
   V(Return, 0x14, _)              \
   V(Unreachable, 0x15, _)
-// TODO(titzer): numbering
 
 // Constants, locals, globals, and calls.
 #define FOREACH_MISC_OPCODE(V) \
@@ -95,7 +96,8 @@ std::ostream& operator<<(std::ostream& os, const FunctionSig& function);
   V(LoadGlobal, 0x10, _)       \
   V(StoreGlobal, 0x11, _)      \
   V(CallFunction, 0x12, _)     \
-  V(CallIndirect, 0x13, _)
+  V(CallIndirect, 0x13, _)     \
+  V(CallImport, 0x1F, _)
 
 // Load memory expressions.
 #define FOREACH_LOAD_MEM_OPCODE(V) \