Implement source debugging for interpreter and AOT (#769)

Implement source debugging feature for classic interpreter and AOT:
- use `cmake -DWAMR_BUILD_DEBUG_INTERP=1` to enable interpreter debugging
- use `cmake -DWAMR_BUILD_DEBUG_AOT=1` to enable AOT debugging

See doc/source_debugging.md for more details.

core/iwasm/libraries/debug-engine/utils.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2021 Ant Group.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#ifndef UTILS_H
+#define UTILS_H
+
+static const char hexchars[] = "0123456789abcdef";
+
+int
+hex(char ch);
+
+char *
+mem2hex(char *mem, char *buf, int count);
+
+char *
+hex2mem(char *buf, char *mem, int count);
+
+int
+unescape(char *msg, int len);
+
+#endif /* UTILS_H */