Address several issues from compiling examples

Compiling the code from examples "code-block:: c" along with public
includes and a bsp exposed a few issues amongst a lot of false
positives. Address some of these:

* Terminate struct declarations with ';'. Mainly for pedantic
  correctness.

* Show ptrdiff_t instead of size_t for the sbrk() prototype, matching
  the current argument type in rtems.

* Replace some occurrences of unsigned16 with uint16_t.

* Fix odd type declaration, "uint8_t char*" -> "char*".

* Use appropriate helper to get chain head instead of invalid access to
  nonexistent struct member.

* Remove several excess '\' escapes.

* Use RTEMS_SELF instead of undefined SELF.

* Use rtems_task instead of void for task functions.

* Add missing stack size parameter in task creation.

* Use rtems_interrupt_level instead of undefined rtems_interrupt.

* Correct return value format for rtems_object_id_get_api()
  rtems_object_id_get_index() (enum and uint16_t) and also fix
  corresponding print formatting.

* Correct return value documentation for rtems_object_id_get_class(),
  rtems_object_id_get_node() and rtems_object_id_get_index()
  int -> uint32_t.

* Use RTEMS_SUCCESSFUL instead of undefined RTEMS_STATUS_SUCCESSFUL and
  fix return value variable name in rate monotonic examples.

* Use RTEMS_TIMEOUT instead of undefined TIMEOUT and RTEMS_PERIOD_STATUS
  instead of undefined STATUS.

* Add missing fields to ftpd configuration.

* Correct parameter types in ftpd hook prototype,
  unsigned char * -> void *.

* Fix various code-block:: attributes, c -> makefile and c -> shell.

* Add missing parenthesis in socket buffer memory calculation example.

* Remove typedef in declaration of mq_attr since it is defiend without
  typedef in reality.

* Update siginfo_t declaration to match current reality.

* Update shell user command definition example to include mode, uid and
  gid.

shell/configuration_and_init.rst

@@ -103,12 +103,15 @@ provided an alias for ``usercmd`` named ``userecho``.
         return 0;
     }
     rtems_shell_cmd_t Shell_USERCMD_Command = {
-        "usercmd",                   /* name */
-        "usercmd n1 \[n2 \[n3...]]", /* usage */
-        "user",                      /* topic */
-        main_usercmd,                /* command */
-        NULL,                        /* alias */
-        NULL                         /* next */
+        "usercmd",                                                   /* name */
+        "usercmd n1 [n2 [n3...]]",                                   /* usage */
+        "user",                                                      /* topic */
+        main_usercmd,                                                /* command */
+        NULL,                                                        /* alias */
+        NULL,                                                        /* next */
+        S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH,   /* mode */
+        0,                                                           /* uid */
+        0                                                            /* gid */
     };
     rtems_shell_alias_t Shell_USERECHO_Alias = {
         "usercmd",                   /* command */

shell/file_and_directory.rst

@@ -100,7 +100,7 @@ NOTES:
 EXAMPLES:
     The following is an example of how to use ``blksync``:
 
-    .. code-block:: c
+    .. code-block:: shell
 
         blksync /dev/hda1
 
@@ -1469,7 +1469,7 @@ ln - make links
 .. index:: ln
 
 SYNOPSYS:
-    .. code-block:: c
+    .. code-block:: shell
 
         ln [-fhinsv] source_file [target_file]
         ln [-fhinsv] source_file ... target_dir
@@ -1729,7 +1729,7 @@ mkdir - create a directory
 .. index:: mkdir
 
 SYNOPSYS:
-    .. code-block:: c
+    .. code-block:: shell
 
         mkdir  dir [dir1 .. dirN]
 

shell/general_commands.rst

@@ -1030,7 +1030,7 @@ time - time command execution
 .. index:: time
 
 SYNOPSYS:
-    .. code-block:: c
+    .. code-block:: shell
 
         time command [argument ...]