Implement native function pointer check, addr conversion and register, update documents (#185)

Modified WASM runtime API:
- wasm_runtime_module_malloc()
- wasm_runtime_lookup_function()
Introduced runtime API
- wasm_runtime_register_natives()

product-mini/platforms/alios-things/aos.mk

@@ -92,7 +92,7 @@ $(NAME)_SOURCES := ${SHARED_ROOT}/platform/alios/bh_assert.c \
                    ${IWASM_ROOT}/common/wasm_native.c \
                    ${IWASM_ROOT}/common/wasm_exec_env.c \
                    ${IWASM_ROOT}/common/arch/${INVOKE_NATIVE} \
-                   src/main.c src/ext_lib_export.c
+                   src/main.c
 
 ifeq (${WAMR_BUILD_INTERP}, 1)
 $(NAME)_SOURCES += ${IWASM_ROOT}/interpreter/wasm_interp.c \

product-mini/platforms/alios-things/src/ext_lib_export.c

@@ -1,10 +0,0 @@
-/*
- * Copyright (C) 2019 Intel Corporation.  All rights reserved.
- * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
- */
-
-#include "lib_export.h"
-
-static NativeSymbol extended_native_symbol_defs[] = { };
-
-#include "ext_lib_export.h"