remove function finsh_set_device in application.c in bsp/stm32f10x

finsh_set_device is not needed since version 1.2.0

fix initialization error in bsp/stm32f10x

temporarily disable canapp initialization.

fix various bugs in lwip-nat

This bug causes buffer overrun.

LWIP_NAT_TMR_INTERVAL_SEC defined in ipv4_nat.h is in miliseconds,
but ip_nat_check_timeout() thinks it's in seconds.

With this bug, all nat entries will expire immediately when
ip_nat_check_timeout() is called.

Note sys_timeout() is in miliseconds.

SCons PreProcessor patch: Stop processing "#define" in false condition

Example "rtconfig.h" content:
 ...
 //#define BOARD_USING_LED
 #if defined(BOARD_USING_LED)
 #define RT_USING_RTGUI
 #endif
 ...

- Before patching, RTGUI module will be built although not intend to do so.
- After patching, RTGUI module will not be built.

fixed Lwip bug: Assert on TCP netconn_write with sndtimeout set

ref: http://savannah.nongnu.org/bugs/?38219

[DFS] Fix the ramfs issue.

修正components.h中使能RT_USING_DFS_RAMFS宏时，加入ramfs.h头文件

[BSP] Add new BSP for STM32F411RE with STM32 HAL Library

1. Target board: STM32F411RE-Nucleo
2. Using STM32 HAL library version 1.4.3 (STM32Cube_FW_F4_V1.10.0)

Update finsh_token.c

修正finsh不能正确处理"\""和"\x1A"转义;