sys: fix doxygen grouping

sys/net/gnrc/routing/rpl/gnrc_rpl_of_manager.c

@@ -10,7 +10,7 @@
 
 /**
  *
- * @ingroup rpl
+ * @ingroup net_gnrc_rpl
  * @{
  * @file
  * @brief   RPL Objective functions manager

sys/net/transport_layer/tcp/tcp_hdr_print.c

@@ -7,6 +7,7 @@
  */
 
 /**
+ * @ingroup     net_tcp
  * @{
  *
  * @file

sys/net/transport_layer/udp/udp_hdr_print.c

@@ -7,7 +7,7 @@
  */
 
 /**
- * @ingroup     net_pktdump
+ * @ingroup     net_udp
  * @{
  *
  * @file

sys/newlib_syscalls_default/syscalls.c

@@ -8,7 +8,9 @@
  */
 
 /**
- * @ingroup     sys_newlib
+ * @defgroup    sys_newlib Newlib system call
+ * @ingroup     sys
+ * @brief       Newlib system call
  * @{
  *
  * @file

sys/posix/time/posix_time.c

@@ -4,8 +4,11 @@
  * This file is subject to the terms and conditions of the GNU Lesser
  * General Public License v2.1. See the file LICENSE in the top level
  * directory for more details.
+ */
+
+/**
+ * @ingroup sys_xtimer
  *
- * @ingroup xtimer
  * @{
  * @file
  * @brief xtimer posix wrapper

sys/ps/ps.c

@@ -7,7 +7,7 @@
  * General Public License v2.1. See the file LICENSE in the top level
  * directory for more details.
  *
- * @ingroup ps
+ * @ingroup sys_ps
  * @{
  * @file
  * @brief   UNIX like ps command

sys/shell/commands/sc_gnrc_rpl.c

@@ -8,7 +8,7 @@
  */
 
 /**
- * @ingroup     sys_shell_commands.h
+ * @ingroup     sys_shell_commands
  * @{
  *
  * @file

sys/xtimer/xtimer.c

@@ -8,7 +8,8 @@
  */
 
 /**
- * @ingroup xtimer
+ * @ingroup sys_xtimer
+ *
  * @{
  * @file
  * @brief xtimer convenience functionality

sys/xtimer/xtimer_core.c

@@ -5,8 +5,11 @@
  * This file is subject to the terms and conditions of the GNU Lesser
  * General Public License v2.1. See the file LICENSE in the top level
  * directory for more details.
+ */
+
+/**
+ * @ingroup sys_xtimer
  *
- * @ingroup xtimer
  * @{
  * @file
  * @brief xtimer core functionality