Avoid using naked braces

ISSOtm · ISSOtm · commit 0937be788a57 · 2020-09-05T13:23:51.000+02:00
They will be removed in an upcoming RGBASM version
diff --git a/structs.asm b/structs.asm
@@ -331,7 +331,7 @@ FIELD_NAME::
                 ds STRUCT_FIELD_SIZE
             ELSE
 
-DATA_TYPE equs STRCAT("D", {{STRUCT_FIELD_TYPE}})
+DATA_TYPE equs STRCAT("D", "{{STRUCT_FIELD_TYPE}}")
 
                 REPT STRUCT_FIELD_NBEL
                     DATA_TYPE \3
