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()

core/iwasm/aot/aot_runtime.h

@@ -141,7 +141,7 @@ typedef struct AOTModule {
     /* is jit mode or not */
     bool is_jit_mode;
 
-#if WASM_ENABLE_JIT
+#if WASM_ENABLE_JIT != 0
     WASMModule *wasm_module;
     AOTCompContext *comp_ctx;
     AOTCompData *comp_data;
@@ -379,7 +379,8 @@ void
 aot_clear_exception(AOTModuleInstance *module_inst);
 
 int32
-aot_module_malloc(AOTModuleInstance *module_inst, uint32 size);
+aot_module_malloc(AOTModuleInstance *module_inst, uint32 size,
+                  void **p_native_addr);
 
 void
 aot_module_free(AOTModuleInstance *module_inst, int32 ptr);
@@ -431,6 +432,13 @@ bool
 aot_is_wasm_type_equal(AOTModuleInstance *module_inst,
                        uint32 type1_idx, uint32 type2_idx);
 
+/**
+ * Invoke native function from aot code
+ */
+void
+aot_invoke_native(WASMExecEnv *exec_env, uint32 func_idx,
+                  uint32 *frame_lp, uint32 argc, uint32 *argv_ret);
+
 uint32
 aot_get_plt_table_size();