[bsp][stm32f0x] Modify build config to reduce code size for Travis CI

x86: fix compile error in c++

[bsp][stm32f03x] Modify build config to reduce code size for Travis CI

[cpu] Split ARM926 cpu code from SAM9260 BSP

2. [bsp][sam9260] Remove unused ld file
3. [bsp][sam9260] Add J-Link debug scripts

1. [bsp][sam9260] Fix the bug that auto reset after boot 20s. Disable watchdog in rt_lovel_level_init function.
2. [bsp][sam9260] Modify SCONS scripts to support IAR tool chain.
3. [bsp][sam9260] Move link strips in to folder link_scripts.
4. [libcpu][arm926] Add copy right to source file and format code.

Fix a regression on 62a0172d.

The old `--keep` parameter for Keil is wrong. RTFM of Keil and get it
right.

Fix keil keep symbol

Fix a regression on 62a0172d.

The old `--keep` parameter for Keil is wrong. RTFM of Keil and get it
right.

[DFS] fix the NFS link issue

[tools] Add package.json as building script.

memheap: check the USED bit in rt_memheap_free

This will ease the debugging of double-free bug.

修正rtt-root位于其他目录时计算目录错误的bug

Use svg instead of png to get better image quality

[DeviceDriver] stm32: Remove explicity clear of RXNE flag

According to STM32 Manual, the USART RXNE flag will be clear automatically after
read to the USART_DR register[1], so the call to USART_ClearITPendingBit is
unnecessary.

[1]: See RM0090 Reference Manual p.992, Bit 5

生成vs文件时将区分编译目录，防止同名的源文件不能编译的情况

update nrf51822 in bsp

[BSP] add nRF51822 BSP.

[DeviceDriver] Fix inverted logic on SConscript