Fold opcode.{c,h} into bytecode.{c,h}

compile.h

@@ -2,13 +2,9 @@
 #define COMPILE_H
 #include <stdint.h>
 #include "jv.h"
-#include "opcode.h"
+#include "bytecode.h"
 #include "locfile.h"
 
-struct bytecode;
-struct symbol_table;
-struct cfunction;
-
 struct inst;
 typedef struct inst inst;