Add eval support for JerryScript debugger (#1588)

The server can accept a string, execute it with eval,
and returns with the result converted to string. In
case of exception it returns with the exception message.

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

jerry-core/debugger/jerry-debugger-ws.h

@@ -27,6 +27,16 @@
  */
 #define JERRY_DEBUGGER_MAX_BUFFER_SIZE 128
 
+/**
+ * Maximum number of bytes can be received in a single message.
+ */
+#define JERRY_DEBUGGER_MAX_SEND_SIZE (JERRY_DEBUGGER_MAX_BUFFER_SIZE - 1)
+
+/**
+ * Maximum number of bytes can be received in a single message.
+ */
+#define JERRY_DEBUGGER_MAX_RECEIVE_SIZE (JERRY_DEBUGGER_MAX_BUFFER_SIZE - 6)
+
 /**
  * Last fragment of a Websocket package.
  */