[Interpreter] Add support for loading globals in the interpreter.

src/interpreter/bytecodes.h

Index: src/interpreter/bytecodes.h
diff --git a/src/interpreter/bytecodes.h b/src/interpreter/bytecodes.h
index f4756516f16f874c248f266af95e32582fd2d829..5b63eec4807c3ca8031d0f6ffdc05ee60a94d72f 100644
--- a/src/interpreter/bytecodes.h
+++ b/src/interpreter/bytecodes.h
@@ -36,6 +36,9 @@ namespace interpreter {
   V(LdaTrue, OperandType::kNone)                                           \
   V(LdaFalse, OperandType::kNone)                                          \
                                                                            \
+  /* Load globals */                                                       \
+  V(LdaGlobal, OperandType::kIdx)                                          \
+                                                                           \
   /* Register-accumulator transfers */                                     \
   V(Ldar, OperandType::kReg)                                               \
   V(Star, OperandType::kReg)                                               \