1. code cleanup for Kconfig.
2. fix the compiling warning for BYTE_ORDER.

1. Remove INIT_FS_EXPORT and change INIT_DEVICE_EXPORT as the first item
in the initalization thread.
2. Move the eth_system_device_init into INIT_PREV_EXPORT item.

1. Add IPADDR/GWADDR etc;
2. Add Kconfig for libcpu.

Use RT_LWIP_IPADDR/GWADDR/MSKADDR to replace old options:
RT_LWIP_GWADDR0/1/2/3 etc.

1. Remove RT_LWIP_USING_RT_MEM option;
2. Add waitqueue patch for lwIP 2.0.2;