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/gdbserver.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2021 Ant Group.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#ifndef _GDB_SERVER_H
+#define _GDB_SERVER_H
+
+#include <stdbool.h>
+
+#define PACKET_BUF_SIZE 0x8000
+
+enum GDBStoppointType {
+    eStoppointInvalid = -1,
+    eBreakpointSoftware = 0,
+    eBreakpointHardware,
+    eWatchpointWrite,
+    eWatchpointRead,
+    eWatchpointReadWrite
+};
+typedef struct WasmDebugPacket {
+    unsigned char buf[PACKET_BUF_SIZE];
+    unsigned int end;
+} WasmDebugPacket;
+
+struct WASMDebugControlThread;
+typedef struct WASMGDBServer {
+    int listen_fd;
+    int socket_fd;
+    WasmDebugPacket pkt;
+    bool noack;
+    struct WASMDebugControlThread *thread;
+} WASMGDBServer;
+
+WASMGDBServer *
+wasm_launch_gdbserver(char *addr, int port);
+
+void
+wasm_close_gdbserver(WASMGDBServer *server);
+
+bool
+wasm_gdbserver_handle_packet(WASMGDBServer *server);
+#endif