Fix Posix demo build and remove src directory (#213)

* Fix: build errors, remove src directory and bring all files up
* Fix: Remove not needed header
* Doc: fix main comments
* Doc: fix comment

Co-authored-by: Alfred Gedeon <gedeonag@amazon.com>

FreeRTOS/Demo/Posix_GCC/TCPEchoClient_SingleTasks.h

@@ -0,0 +1,40 @@
+/*
+ * FreeRTOS Kernel V10.3.0
+ * Copyright (C) 2017 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * http://www.FreeRTOS.org
+ * http://aws.amazon.com/freertos
+ *
+ * 1 tab == 4 spaces!
+ */
+
+#ifndef SINGLE_TASK_TCP_ECHO_CLIENTS_H
+#define SINGLE_TASK_TCP_ECHO_CLIENTS_H
+
+/*
+ * Create the TCP echo client tasks.  This is the version where an echo request
+ * is made from the same task that listens for the echo reply.
+ */
+void vStartTCPEchoClientTasks_SingleTasks( uint16_t usTaskStackSize, UBaseType_t uxTaskPriority );
+BaseType_t xAreSingleTaskTCPEchoClientsStillRunning( void );
+
+#endif /* SINGLE_TASK_TCP_ECHO_CLIENTS_H */
+
+