Fix multiple debugger issues. (#1640)

- Wait for free byte code pointers during garbage collection.
- Detect incorrect free requests in the debugger server.
- Ignore byte code blocks loaded from snapshot.
- Use memmove instead of memcpy to avoid receive buffer corruption.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/debugger/jerry-debugger.h

@@ -98,9 +98,8 @@ typedef enum
  */
 typedef struct
 {
-  uint16_t size;
-  jmem_cpointer_t prev_cp;
-  jmem_cpointer_t next_cp;
+  uint16_t size; /**< size of the byte code header divided by JMEM_ALIGNMENT */
+  jmem_cpointer_t prev_cp; /**< previous byte code data to be freed */
 } jerry_debugger_byte_code_free_t;
 
 /**