Implement multi-module feature and bulk-memory feature (#271)

Refine wasm loader and aot loader
Fix potential issue of os_mmap/os_munmap
Update document

core/config.h

@@ -94,6 +94,11 @@ enum {
 #define WASM_ENABLE_APP_FRAMEWORK 0
 #endif
 
+/* Bulk memory operation */
+#ifndef WASM_ENABLE_BULK_MEMORY
+#define WASM_ENABLE_BULK_MEMORY 0
+#endif
+
 /* WASM log system */
 #ifndef WASM_ENABLE_LOG
 #define WASM_ENABLE_LOG 1
@@ -120,6 +125,11 @@ enum {
 #define WASM_ENABLE_OPCODE_COUNTER 0
 #endif
 
+/* Support a module with dependency, other modules */
+#ifndef WASM_ENABLE_MULTI_MODULE
+#define WASM_ENABLE_MULTI_MODULE 0
+#endif
+
 /* Heap and stack profiling */
 #define BH_ENABLE_MEMORY_PROFILING 0