Support emit specified custom sections into AoT file (#1207)

And add API to get the content of custom section with
section name for both wasm file and aot file.

core/iwasm/interpreter/wasm_loader.h

@@ -73,6 +73,11 @@ wasm_loader_find_block_addr(WASMExecEnv *exec_env, BlockAddr *block_addr_cache,
                             uint8 block_type, uint8 **p_else_addr,
                             uint8 **p_end_addr);
 
+#if WASM_ENABLE_LOAD_CUSTOM_SECTION != 0
+void
+wasm_loader_destroy_custom_sections(WASMCustomSection *section_list);
+#endif
+
 #ifdef __cplusplus
 }
 #endif