update libcpu/arm/cortex-m4: support lazy stack optimized.

回收main函数所用的栈空间

tools: add an option to generate cscope database

When --cscope option is given to Scons, it will generate a cscope
cross-reference database in current directory, which is useful in
Vim(and other cscope-aware text editors). For example, `scons -s
--cscope` will do nothing except generating the database. You can use
this option with other options together.

It is inspired by the `make cscope` of Linux.

Rm48x50

format s3c24x0 serial.c and mini2440 rtconfig.py

format the s3c24x0 serial.c and mini2440 rtconfig.py

完善生成codeblock工程功能。

indent format cortex-m3/cpuport.c, thank peter.uboot@gmail.com

Signed-off-by: Nvisitor83 <root@wolflouis.(none)>

udisk can be ejected

usb: add USB_MSG_PLUG_OUT event

Some driver will emit USB_MSG_DATA_NOTIFY before the USB get configured.
Filter out those events.

When the core received an USB_MSG_PLUG_OUT event, it will stop all the
classes. This make a chance that the classes could get rid off doing
useless stuff while the USB cable is plugged out.