Remove the stdarg.h file include.

Please @Grissiom check why add this header file in rtthread.h.
rename group of logtrace
Use lwIP 1.4.1 as the default TCP/IP protocol stack
Move logtrace to utilites
add sys_now() function porting
fix lwip 1.4.1 compiling error when enable component init
rm48x50: restore missing include for __TI_COMPILER_VERSION__
Merge pull request #115 from grissiom/rm48x50

rm48x50: restore missing include for __TI_COMPILER_VERSION__
remove RT_LWIP_TCP_SND_BUF setting

When not configured in rtconfig.h, lwipopt.h will give us a reasonable
value(TCP_MSS * 2).
Merge pull request #117 from grissiom/fix-sam7x

remove RT_LWIP_TCP_SND_BUF setting
Add device checking when set_device.