Add payload to evm_result (stupid name)

examples/examplevm.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include <evm.h>
 #include "evm.h"
 
 
@@ -93,7 +94,7 @@ static struct evm_result execute(struct evm_instance* instance,
         ret.output_data = output_data;
         ret.output_size = address_size;
         ret.release = &free_result_output_data;
-        ret.context = NULL; // We don't need another pointer.
+        ret.payload.pointer = NULL; // We don't need another pointer.
         return ret;
     }
     else if (code_size == strlen(counter) &&

include/evm.h

@@ -169,12 +169,12 @@ struct evm_result {
     /// function to the result itself allows EVM composition.
     evm_release_result_fn release;
 
-    /// The optional pointer to an internal EVM context.
-    ///
-    /// This field MAY be used by _EVM implementations_ to store additional
-    /// result context (e.g. memory buffers). The pointer value MUST NOT
-    /// be accessed nor changed by EVM users.
-    void* context;
+    /// Reserved data to be optionally used by implementations.
+    union {
+        uint8_t bytes[24];
+        struct evm_uint160be address;
+        void* pointer;
+    } payload;
 };
 
 /// The query callback key.